CHAPTER V

GENERAL ZOOLOGICAL WORK

In the course of the preceding chapters numerous more or less incidental references have been made to the contributions of Sir William Flower to biological literature, as well as to his many improvements in museum organisation and arrangement. The more detailed discussion of these has, however, been reserved for the present and succeeding chapters, of which the first two are devoted to the zoological and the third to the anthropological side of his work, while in the fourth his views in regard to museums and certain other subjects are taken into consideration.

Regarding the general scientific work of Flower, it must be confessed at the outset that this is characterised in the main by its conscientious carefulness and exactness, rather than by brilliancy of thought, conception, or style. Great attention to detail, both as regards the work itself and in reference to authorities (which were always most carefully verified), is indeed one of the leading features of his labours; but there is no epoch-making discovery or comprehensive generalisation which can be associated with his name. In connection with his careful attention to small and apparently trivial points of detail, the following passage from Professor Ray Lankester’s obituary notice in _Nature_ may be appropriately quoted:—

“He did his own work with his own hands, and I have the best reason to know that he was so deeply shocked and distressed by the inaccuracy which unfortunately crept into some of the work of his distinguished predecessor, Owen, through the employment of dissectors and draughtsmen, whose work he did not sufficiently supervise, that he himself determined to be exceptionally careful and accurate in his own records and notes.”

In another passage of his notice the same writer observes that:—

“Caution and reticence in generalisation certainly distinguish all Flower’s scientific writings. Whilst he was on this account necessarily not known as the author of stirring hypotheses, his statements of fact gained in weight by his reputation for judgment and accuracy.”

Flower’s zoological studies related entirely to the vertebrates and almost exclusively to mammals, although he devoted a few papers, such as the one on the gular pouch of the great bustard, and that on the skull of a cassowary, to birds. Other groups, I believe, he never touched. In the earlier years of his scientific career, at anyrate, his labours were in the main devoted to the anatomical aspect of zoology, such subjects as the dentition, osteology, and the structure and characters of the brain and viscera claiming a much larger share of his attention than was bestowed on the myology. In latter years the classification of the major groups of the mammalia received much attention from Flower. Not that he was in any way what is nowadays called a systematist in zoology, that is to say, he took no active part in describing new species (not to mention sub-species, which had scarcely begun to be recognised by naturalists in his day), or the redefining of generic groups, and other work of this nature. Indeed, as mentioned in the chapter devoted to his career at the College of Surgeons, he was extremely conservative in this respect, and strongly opposed to the modern fondness for small generic groups, and also for changing generic names which, from long association, have come almost to be regarded as household words and integral parts of the English language. The substitution of the name _Procavia_, for _Hyrax_, the familiar title of the Klipdass, was, for instance, very repugnant to him, although loyally accepted when found to be coming into general use.

As a matter of fact, so far as my information goes, with the exception of certain whales and dolphins, and one extinct sea-cow (_Halitherium_), Flower never named a new species of animal, nor, I think, did he ever propose a new generic term. Indeed, so opposed was he to any interference with names of the latter description in general use, that when several such were replaced by alternative ones in the _Study of Mammals_, it was expressly stipulated by him that the responsibility for such substitution should rest solely with the present writer.[3]

The modern system of forming trinomials to indicate the local races, or sub-species, of mammals (as exemplified by _Giraffa camelopardalis rothschildi_ and _Giraffa camelopardalis capensis_ for two of the local phases of the species of giraffe typified by _G. camelopardalis_ of the Egyptian Sudan and Abyssinia), was practically in its infancy during the active life-time of Flower, and it is doubtful how he would have approved of the extent to which it has been subsequently carried. Nevertheless, that he appreciated the practice of recognising minute local differences of colour, size, etc., in the same species of mammals is evident from an incident within the writer’s own knowledge, which occurred at the Natural History Museum, when a tray containing the local phases of one of the species of the small squirrel-like rodents known as chipmunks was submitted to his notice; his remark being that such variations from a common type ought in nowise to be ignored, if we wished to make our knowledge of animals anything like complete, and that the simplest way of indicating such differences was to assign them distinct names.

In a general way, however, it may be said that Sir William’s sympathies were with the wider and more philosophical aspects of zoology rather than with the details of specific and sub-specific distinction (which, by the way, have scarcely any more right to be regarded as real philosophical science than has stamp-collecting)[4]; and that, from a systematic standpoint, his interest was very largely concentrated on the relationships existing between the mammals of to-day and their extinct predecessors. Several of his lectures and papers, and one especially of his separate works (that on _The Horse_) were indeed devoted to this aspect of the subject; and on every possible occasion he emphasised his conviction of the necessity of studying (and arranging in museums) living and extinct mammals together, if we wish to make our science really practical.

As a matter of fact he had the strongest possible objection to the recognition of “palæontology” as a science apart from zoology, and he even went so far as to mildly rebuke (in his own inimitably courteous and gentle manner) the present writer, for venturing to offer to the public a volume on that subject. To a great extent, no doubt, he was perfectly right in this contention, although there are points of view from which “palæontological” works are decidedly convenient, even if their existence and production cannot be logically justified.

As regards the particular groups of mammals (other than man) in which Flower was more especially interested, there can be no doubt that the Cetacea (whales and dolphins) occupied the first position. And on this subject he was undoubtedly one of the first authorities, his only possible rivals in this country, at anyrate, being Sir William Turner and Professor Struthers. Next to this group came, perhaps, the marsupials, in which a most important discovery was made by Flower in regard to the succession and replacement of the teeth.

Not even the most sympathetic of biographers would attempt for one instant to assume that his hero—if a zoologist—could by any possibility be infallible; and it has to be recorded that many changes and amendments have had to be made in Flower’s conclusions. Perhaps, indeed, Sir William has been to some extent especially unfortunate in this respect, owing to the extreme imperfection of the state of our palæontological (I must use the objectionable word) knowledge at the date when much of his best work was accomplished. At that time, in spite of the enormous and valuable results achieved by Cuvier, Owen, and others, mammalian palæontology may be said to have been in its infancy compared to its present state; the wonderful discoveries in North and South America being then either unknown or only partially revealed, and the same being the case with regard to those made known by the working of the phosphorite beds in Central France.

These and other discoveries have, for instance, totally revolutionised our ideas with regard to the affinities of the different families of the modern Carnivora, and have thus led to considerable modifications of the views entertained by Flower as to the relationships of the members of this group.

Moreover, there is another important factor which has to be taken into consideration. At the time when Sir William wrote his celebrated memoir on the Carnivora, the effects of what is now universally known among zoologists as “parallelism in development” were quite unrecognised. By “parallelism” (to abbreviate the expression) is meant, it may be explained, a remarkable tendency which undoubtedly exists among animals of markedly diverse origin to become more or less like one another in at least one important structural feature, when living under similar physical conditions, or specially adapted for similar modes of existence. Not unfrequently this structural resemblance, when closely examined, is found to be less close than might at first sight have seemed to be the case; the adaptation having been brought about by the modification of structures originally more or less dissimilar towards a common type. In other words, the same goal has been reached by two different routes.

An excellent example of this is offered by the development of “cannon-bones” in the lower portion of the limbs of the members of the horse tribe on the one hand and those of the deer and antelopes on the other; the object of this lengthening and strengthening of this part of the limb being in both instances the attainment of increased speed. Whereas, however in the one instance the cannon-bone is formed from one original element, in the other it is the result of the fusion of two such elements. In this case, indeed, the difference in the structure of this part of the skeleton in the two groups is so apparent as to leave no reasonable doubt as to the remoteness of the affinity between their respective ancestors. There is, however, a certain group of extinct South American hoofed mammals in which the cannon-bone corresponds exactly in origin and structure with that of the horse, from which it might be assumed that the two animals were closely related, whereas, from other evidence, we know that they are widely sundered. Approximately similar structures are therefore in many instances far from being indications of genetic affinity between the animals in which they respectively occur. Before the occurrence of this parallelism was recognised by naturalists as an important factor in their development, such resemblances were, however, frequently regarded as indications of a common parentage, so that animals which had comparatively little to do with one another were brigaded as members of the same assemblage.

With these preliminary remarks, we may proceed to a general survey of Sir William’s zoological work. It has, however, been found convenient to relegate the consideration of his numerous memoirs on the Cetacea to the next chapter, by which means their connection will be made more apparent than if they were discussed among those on other sections of zoology.

The first zoological paper (and indeed the first scientific work of any description) published by Flower seems to have been that on the dissection of one of the African lemurs belonging to the genus _Galago_, which appeared in the Zoological Society’s _Proceedings_ for 1852, and serves to prove, as mentioned in the first chapter, that the author was at that time holding the post of Curator of the Museum of the Middlesex Hospital. The paper itself is of little importance, dealing only with the structure of the muscles and viscera of the species in question.

The next paper on the list, which appeared in the same journal for 1860, was also written during this part of Flower’s career; it is one of the few devoted to the anatomy of birds, and describes the gizzard of the Nicobar pigeon and other graminivorous species.

About this time Flower began to devote his attention to the mammalian brain; his first contribution on this subject being “Observations on the Posterior Lobes of the Cerebrum of the Quadrumana, with the Description of the Brain of a _Galago_,” of which an abstract appeared in the _Proceedings_ of the Royal Society of London for 1860, although the complete memoir was not published till 1862, in the _Philosophical Transactions_. The date of publication of the abstract proves that these studies were commenced, and the memoir in question completed, before (and not, as stated by Professor M’Intosh,[5] after) the author’s appointment to the Conservatorship of the Museum of the College of Surgeons, which did not take place till the year 1861. The brain of another monkey was also described in a paper on the anatomy of a South American species then known as _Pithecia monachus_, which appeared in the Zoological Society’s _Proceedings_ for 1862. In the following year (1863) he published, in the _Natural History Review_, a still more important communication, dealing with the brain of the Malay siamang (_Hylobates syndactylus_), one of the man-like apes, in which it was shown that in this species (and probably therefore in gibbons generally) the posterior part of the cerebrum, or main division of the brain, overlapped the cerebellum, or hind brain, to an even less degree than in the American howling-monkeys, which had hitherto been regarded as the lowest members of the group, so far as the feature in question was concerned. That such a feature should occur in one of the highest groups of apes was certainly a remarkable and unexpected discovery. Yet another contribution to the same subject was made in 1864, when a paper appeared in the Zoological Society’s _Proceedings_ on the brain of the red howling-monkey, then known as _Mycetes seniculus_, but of which the generic title is changed by many modern naturalists to _Alouata_.

The earlier memoirs of this series published (in the _Philosophical Transactions_), writes Professor M’Intosh in the _Scottish Review_ for 1900, “formed important evidence in the discussions which took place between Owen and Huxley in regard to the posterior lobe of the brain, the posterior cornu, and the hippocampus minor.” Professor Owen, at the Cambridge Meeting of the British Association in 1862, maintained, from specimens of the human brain in spirit, and from a cast of the interior of the gorilla’s skull, that in man the posterior lobes of the brain overlapped the cerebellum, whereas in the gorilla they did not; that these characters are constant, and therefore he had decided to place man, with his overlapping posterior lobes, the existence of a posterior horn in the lateral ventricle, and the presence of a hippocampus minor in the posterior horn, under the special division Archencephala. Moreover, he grouped with these features the distinctive characters of the foot of man, and showed how it differed from that of all monkeys. Flower’s accurate investigations enabled Huxley to substantiate his antagonistic position to Owen’s doctrines, viz., that these structures, instead of being the attributes of man, are precisely the most marked cerebral characters common to man with the apes. Huxley also asserted that the differences between the foot of man and that of the higher apes were of the same order, and but slightly different in degree from those which separated one ape from another.

The result of this controversy was the overthrow (except in the mind and works of its author) of Owen’s separation of man on the one hand as the representative of a primary group—the Archencephala; and of apes, monkeys, Carnivora, Ungulates, Sirenians, and Cetaceans on the other hand, as forming a second group—the Gyrencephala.[6] As will be seen from the above quotation, this result was very largely due to the work of Flower, although it was brought into prominent notice by the superior fighting powers of Huxley, who was also an older, and at the time at anyrate, a better-known man. It may be added that Flower himself subsequently abandoned the use of the term “Quadrumana,” as distinguishing apes and monkeys on the one hand from man, as “Bimana,” on the other, and brigaded all altogether under their Linnæan title “Primates.”

The contributions of Flower to our knowledge of (and, it may be added, to the clearing up of misconceptions in regard to) the mammalian brain, was, however, by no means confined to the Primates (man, apes, monkeys, and lemurs). On the contrary, his researches were of equal—if not indeed of more—importance with regard to the structure of that organ in the lower groups of the class, namely the marsupials and the monotremes (duckbill platypus and spiny ant-eater).

In the well-known Reade Lecture of 1859, Professor Owen expressed himself as follows with regard to the brain of the two groups last mentioned:—

“Prior to the year 1836, it was held by comparative anatomists that the brain in mammalia differed from that in all other vertebrate animals by the presence of the large mass of transverse white fibres called ‘corpus callosum’ by the anthropotomist; which fibres, overarching the ventricles and diverging as they penetrate the substance of either hemisphere of the cerebrum, bring every convolution of the one into communication with those of the other hemisphere, whence the other name of this part—the ‘great commissure.’ In that year I discovered that the brain of the kangaroo, the wombat, and some other marsupial quadrupeds, wanted the ‘great commissure’; and that the cerebral hemispheres were connected together, as in birds, only by the ‘fornix’ and ‘anterior commissure.’ Soon afterward I had the opportunity of determining that the same deficiency of structure prevailed in the _Ornithorhynchus_ (duckbill) and _Echidna_ (spiny ant-eater).”

Owen’s conclusions with regard to the absence of the great connecting band of fibres between the hemispheres of the marsupial brain were first published in the _Philosophical Transactions_ for 1837; those, with regard to the same lack in the monotremes, being added in Todd’s _Cyclopædia of Anatomy and Physiology_, Article “Monotremata.” In the latter article it was also stated that the brain of the echidna was further distinguished from that of other mammals by the circumstance that whereas in the latter the portion of the brain known as the optic lobes consists of four lobes (_corpora quadrigemina_), in the echidna and duckbill there are only a pair of such lobes (_corpora bigemina_.)

In consequence of this supposed lack of the corpus callosum in their brains, Owen separated the marsupials and monotremes from other mammals in a primary group by themselves, under the title of Lyencephala.

Flower’s attack on these conclusions was commenced by a paper which appeared in the Zoological Society’s _Proceedings_ for 26th January 1864, entitled “On the Optic Lobes of the Brain of the Echidna,” in which it was conclusively demonstrated that these structures resembled those of the higher mammals in being four-lobed.

More important still was his memoir “On the Commissures of the Cerebral Hemispheres of the Marsupialia and Monotremata, as compared with those of the Placental Mammals,” which was published in the _Philosophical Transactions_ of the Royal Society for 1865. In this was shown, it was thought, the existence in both monotremes and marsupials of a distinct, although very small, corpus callosum connecting the two hemispheres of the brain; the anterior commissure, which in the higher mammals is the smaller connecting band, being in this instance much the larger.

Recent researches have, however, tended to show that Owen was after all right in denying the existence of a corpus callosum in the latter groups. Even allowing for this correction, the result of this important paper was to discredit among all zoologists capable of forming an adequate opinion on the subject Owen’s proposed fourfold division of the Mammalia into Lyencephala, Lissencephala, Gyrencephala, and Archencephala. And these terms have now completely disappeared from zoological literature.

In those days it required no considerable amount of courage to attack a man of Owen’s established social and scientific position on an important subject like this; and Flower’s triumph was therefore the more conspicuous. Of course such of these discoveries as are valid, if they had not been made by him, would have been made later on by somebody else, as they merely required accurate dissection and observation. But this may be said of every discovery of a like nature; and Flower is entitled to all credit for having worked out the subject in the way he did. It may be added, that, with our present knowledge of mammalian morphology, a classification based on the characters of the brain is manifestly based on a misconception from first to last; the degree of development and specialisation of that organ being purely adaptive features, and therefore not dependent upon structural relationships. Had Owen’s classification been maintained, it would have been necessary to assign the primitive Carnivora and Ungulata to a group quite apart from the one containing their existing representatives.

In the light of modern research, it cannot now be held that the result of Flower’s investigations in this direction was to demonstrate the existence of a corpus callosum to the brain in all the members of the mammalian class.

In another paper, dealing with the brain of the Javan loris, published in the _Transactions_ of the Zoological Society, Flower made a further contribution to the study of this part of the organism. Previous to the appearance of the memoir on the marsupial and monotreme brain, Flower had published, in the _Natural History Review_ for 1864, one on the number of cervical vertebræ in the Sirenia (manati and dugong). Apart from several papers on whales and dolphins, which, as already mentioned, are reserved for consideration in a later chapter, the next noteworthy zoological contribution from Flower’s pen appears to be one on the gular pouch of the great bustard, published in the Zoological Society’s _Proceedings_ for 1865. This pouch, which, it may be observed is confined to the cock-bird, and inflated during the breeding season, is a very remarkable structure, which has recently been described in greater detail by Mr. W. P. Pycraft.

Two years later (1867), Flower contributed to the same journal a paper on the anatomy of the West African chevrotain, _Hyomoschus aquaticus_, or, as it is now called, _Dorcatherium aquaticum_. The specimen on which the paper was based was the first of its kind which had ever been dissected—at least in this country; and the result of its examination was to confirm the view that the mouse-deer, or chevrotains, cannot be included among the true ruminants, or Pecora, but rather that they form a group (Tragulina), in many respects intermediate between the latter and the pigs and hippopotamuses, or Suina. To the essential difference between the chevrotains and the musk-deer, which have often been confounded, Flower was very fond of recurring in his later writings.

About the year 1866 Sir William began to turn his attention to the teeth of mammals, more especially as regards the mode in which the milk or baby series is succeeded by the permanent teeth, and the general homology of the milk with the permanent, and of the individual teeth of both series with one another. As the result of these investigations he published during the next few years the following papers on this subject. First and most important, one on the development and succession of the teeth of marsupials, which appeared in the _Philosophical Transactions_ for 1867. In the following year he delivered before the British Association at Norwich a paper entitled “Remarks on the Homologies and Relation of the Teeth of the Mammalia,” which was published in the _Journal of Anatomy and Physiology_ for the same year. In that year he also published, in the _Proceedings_ of the Zoological Society, an account of the homology and succession of the teeth in the armadillos. A general sketch from his pen of the dentition of mammals was published in the _British Medical Journal_ for 1871, while in the _Transactions_ of the Odontological Society for the same year, appeared a paper on the first, or milk, dentition of the Mammalia.

By far the most important of this series of papers is undoubtedly the one on the succession and homologies of the teeth in the marsupials or pouched mammals; and it is the one which contains, perhaps, the most noteworthy discovery made by Flower.

Owen had previously pointed out that marsupials differ from ordinary placental mammals in having four (in place of three) pairs of cheek-teeth at the hinder part of the series which have no milk, or deciduous, predecessors, and are therefore, according to the usual rule, to be regarded as true molars, in contradiction to premolars, in which such deciduous predecessors are generally developed. He considered, however, that all the premolars in the kangaroo (and therefore presumably in other marsupials) as well as the incisors or cutting teeth, and the canines or tusks, were preceded by milk-teeth. Flower, on the other hand (who it is only just to add had a much fuller series of specimens of young marsupials on which to work than was available to Owen), was enabled to show that in the Marsupialia only one pair of teeth in each jaw, at most, is preceded by a milk-tooth. The tooth, in question, is the fifth from the posterior end of the series, and whereas in the adult animal it differs in character from those behind it, its deciduous predecessor resembles the latter. The replacing tooth was further considered to correspond with the fourth or last premolar of placental mammals, while the replaced tooth was regarded as the only one in the entire series corresponding to the milk-teeth of placental mammals. This view rendered it necessary, of course, to regard all the four pairs of cheek-teeth behind this abnormal one as corresponding to the true molars of placentals, as had been done by Owen, thus making, as already mentioned, marsupials to differ from ordinary placentals by possessing four instead of three pairs of these teeth.

Before proceeding to notice an amendment which has been proposed in regard to the homology of the one successional tooth of the marsupials, certain other features connected with it and its predecessor discussed by Flower may be briefly mentioned. He noticed, to quote from an admirable epitome of his observations on this point, drawn up by Professor M’Intosh in the _Scottish Review_ for 1900, “that there were considerable differences in the various genera as to the relative period of the animal’s life at which the fall of the temporary molar and the evolution of its successor takes place. In some, as in the rat-kangaroos, it is one of the latest, the temporary tooth retaining its place and its functions until the animal has nearly, if not quite, reached its full growth, and is not shed until all the other teeth are in position and use. On the other hand, in the Tasmanian wolf the temporary tooth is very rudimentary in size and form, and is shed or absorbed before any other teeth enter the gum. Anterior to the period of Sir William Flower’s communication, mammals had been, in regard to the succession of their teeth, divided into two groups—the Monophyodonts, or those that generate a single series of teeth, and the Diphyodonts, or those that develop two sets of teeth, but, as he pointed out, even in the most typical Diphyodonts the successional process does not extend to the whole of the teeth, always stopping short of those situated most posteriorly in each series. The pouched animals (marsupials), he stated, occupied an intermediate position, presenting, as it were, a rudimentary diphyodont condition, the successional process being confined to a single tooth on each side of each jaw.”

All this is unexceptionable. Flower, however, went further than this, and claimed that the true molar teeth of mammals correspond serially with the permanent premolars, canines, and incisors, and not with their deciduous predecessors. And he therefore urged (as indeed must be the case on these premisses) that the whole dentition of adult marsupials corresponds with the permanent dentition of placentals. A further inference from this is that the milk-teeth, instead of being an original development, may rather be a set superadded to meet the temporary needs of mammals whose permanent set is of a highly complex type.

To review the objections which have been raised against these views would be entering on a very difficult question, and one in regard to which uniformity of opinion by no means exists among naturalists even at the present day. It may be mentioned, however, that from the circumstance of the later milk-premolars resembling (as was noticed by Flower in the case of the one tooth replaced in marsupials) the true molars rather than the permanent premolars, it has been suggested that the milk-dentition is serially homologous with the true molars. And on this view, the entire dentition of marsupials (with the exception of the one replacing tooth) corresponds to the milk-dentition of placentals. Possibly, however, the larger number of incisors which distinguish many of the carnivorous marsupials from the placentals may be due to the development of teeth belonging to the permanent series with those of the milk-set, and both persisting together throughout life. Be this as it may, it is evident, on the above view of the serial homology of their dentition, that marsupials, instead of as Flower supposed, showing the commencement of a milk-dentition, really exhibit the decadence of the permanent series.

In this respect they display a precise similarity to the modern elephants, as indeed was pointed out by Flower in his original paper, although on a false premiss, for he at that time regarded the anterior cheek-teeth of the elephant as the representatives of the permanent premolars, whereas they really correspond with the milk-premolars.

One objection has indeed been raised with regard to the identification of the adult marsupial dentition with the milk-set of placentals, namely, the existence in certain marsupialia of rudimentary teeth belonging to an earlier set than the one functionally developed. This has been got over by regarding these rudimentary germs as the representatives of a prelacteal series.

Passing on to another point, it has to be noticed that exception has also been taken to Flower’s view that the replacing tooth of marsupials and its deciduous predecessor correspond to the fourth, or last premolar of placentals. The question has been discussed in considerable detail in the Zoological Society’s _Proceedings_ for 1899 by the present writer, who had for material the dentition of certain extinct South American mammals quite unknown to science at the time Flower’s paper was written. The result of these comparisons was to render it evident, in the present writer’s opinion, that the replacing tooth of the marsupials corresponds to the third, instead of to the fourth, premolar of placentals. From this it follows that marsupials agree with placentals in possessing only three pairs of true molars; the first of the four teeth in the former behind the replacing tooth being the last milk-premolar (which is never replaced) instead of, as supposed by Flower, the first true molar. This conclusion, as pointed out by the present writer in the paper referred to above, had really been arrived at years previously by Owen, who also believed the replacing tooth to correspond to the third premolar of placentals.

In thus bringing marsupials into line with placentals as regards their dentition, this later interpretation accords well with recent discoveries in regard to other parts of the organisation of the former animals. It should, however, be mentioned that the newer view is by no means accepted by all zoologists, although it has received the support of the well-known American paleontologist, Dr. J. L. Wortman,[7] who is specially qualified to form a trustworthy opinion on a point of this nature.

Finally, whatever be the eventual verdict as to the serial homology of the marsupial dentition as a whole, and also as to that of the replacing premolar, Flower must always be credited with the discovery that marsupials replace only a single pair of teeth in each jaw by vertical successors.

The other papers on dentition referred to above as having been written by Flower about the same time are, although interesting in their way, of far less importance than the one published in the _Philosophical Transactions_. Indeed the one read before the British Association in 1868 and published in the _Journal of Anatomy and Physiology_ for the same year, is little more than a recapitulation of the results arrived at in the former.

The paper on the development and succession of the teeth in the armadillos, published in the Zoological Society’s _Proceedings_ in 1868, is, on the other hand, of considerable interest on account of its confirming the fact first mentioned by the French zoologist, Professor Paul Gervais, but generally overlooked by subsequent writers up to that time, that the common nine-banded armadillo (_Tatusia peba_) differs from its relatives in replacing some of its teeth by vertical successors. This at the time was an unexpected feature in any member of the so-called Edentate mammals; and tended further to break down the supposed hard and fast distinction between monophyodonts and diphyodonts.

Closely connected with the subject of dentition is a paper on “The Affinities and Probable Habits of the Extinct Marsupial, _Thylacoleo carnifex_ (Owen),” communicated by Flower to the Geological Society of London in 1868, and published in the _Quarterly Journal_ of that body for the same year. After alluding to the paper on marsupial dentition, Professor Ray Lankester, in his obituary notice of Sir William in _Nature_, of 13th July 1899, observes of the communication under consideration that—“The next most striking discovery which we owe to Flower seems to me to be the complete and convincing demonstration that the extinct marsupial, called _Thylacoleo carnifex_ by Owen, was not a carnivore, but a gnawing herbivorous creature like the marsupial rats and the wombat—a demonstration which has been brought home to the eye even of the unlearned by the complete restoration of the skull of _Thylacoleo_ in the Natural History Museum by Dr. Henry Woodward.”

If we are to believe later authorities, Flower’s demonstration of the herbivorous nature of the creature in question was by no means so “complete and convincing” as the learned Professor would have us believe; but of this anon.

The first important paper on _Thylacoleo_, which was a creature of the approximate size of a jaguar, whose remains are met with in the superficial formations of Australia, was one by Owen, published in the _Philosophical Transactions_ for 1859. From the general characters of the skull (which was at that time only known by fragments), and especially from the rudimentary condition of the hinder cheek-teeth and the enormous size of the secant replacing premolar, which bears a certain superficial resemblance to the carnassial tooth of the cats, its describer was led to the conclusion that _Thylacoleo_ was a marsupial carnivore, and “one of the fellest and most destructive of predatory beasts.” Probably Owen’s views at this time were, that the creature had its nearest living relatives in the members of the Australian family _Dasyuridæ_, such as the Tasmanian devil (_Sarcophilus ursinus_), and that it bore a relationship to the existing carnivorous marsupials somewhat similar to that presented by a lion to a dog. At this time there was no evidence to show whether the large teeth near the front of the jaw, the existence of which was indicated in the original specimen merely by its empty socket, was a canine or an incisor; and though Owen was inclined to regard it as the former, he admitted that it might be an incisor, in which event he recognised that the affinities of the animal would be more with the herbivorous, or diprotodont section of the marsupials, and more especially the phalangers, or so-called opossums of the colonists. This is clearly indicated by the following sentence appended by Sir Richard to his description:—“If, however, this be really the foremost tooth of the jaw, it would be one of a pair of terminal incisors according to the marsupial type exhibited by the _Macropodidæ_ (kangaroos) and _Phalangistidæ_ (phalangers).”

In 1866, after receiving additional specimens from Australia, Owen was enabled to describe the greater part of the skull and the entire dentition of _Thylacoleo_. The large anterior teeth were clearly recognised to be incisors, which, in Owen’s opinion, “proved the _Thylacoleo_ to be the carnivorous modification of the more common and characteristic type of Australian marsupials, having the incisors of the lower jaw reduced to a pair of large, more or less procumbent and approximately conical teeth, or ‘tusks.’” Not only did the additional evidence serve to confirm Sir Richard in his view of the carnivorous propensities of _Thylacoleo_, but he considered that in this extinct form we have “the simplest and most effectual dental machinery for predatory life and carnivorous diet known in the mammalian class. It is the extreme modification, to this end, of the diprotodont type of marsupialia.”

Beyond, however, admitting its affinities with the diprotodonts, Sir Richard Owen does not appear in this later paper to have regarded _Thylacoleo_ as a near relative of any of the existing forms; but in the article on “Paleontology” in the eighth edition of the _Encyclopædia Britannica_, published in 1859, he seems to have considered it allied to _Plagiaulax_ of the Purbeck strata of Dorsetshire, which had been shown by Dr. Hugh Falconer to be probably of herbivorous habits.

Sir William Flower, in the aforesaid paper in the Geological Society’s _Quarterly Journal_ for 1868, while agreeing with Owen that _Thylacoleo_ was related to the diprotodont rather than to the polyprotodont carnivorous marsupials, differed from the conclusion that it was a carnivore. While the large cutting premolar teeth were considered by Owen to resemble the carnassial teeth of a lion, Flower was struck by their similarity to the corresponding teeth of the rat-kangaroos and the phalangers. After discussing the other teeth, he concluded that “in the number and arrangement of these teeth ... _Thylacoleo_ corresponds exactly with the modern families _Macropodidæ_ and _Phalangistidæ_, and differs completely from the carnivorous marsupials.”

After alluding to the small size of the brain-cavity and the large space for the attachment of the powerful muscles which worked the lower jaw, and suggesting that these features may be only to be expected in a large form as compared with the smaller members of the same group, Flower concluded that the habits of all species with the same general type of dentition must necessarily be similar. And, on these premisses, it was urged that _Thylacoleo_ must in all probability have been a vegetable-feeder. The large premolar may seemingly have been “as well adapted for chopping up succulent roots and vegetables, as for dividing the nutritive fibres of animal prey.” It is further suggested that the nutriment of _Thylacoleo_ “may have been some kind of root or bulb; it may have been fruit; it may have been flesh.” While in conclusion it is argued that the organisation of the animal did not countenance the idea of its preying on the large contemporary marsupials.

Omitting reference to Owen’s reply to this reversal of his conclusions, and also to certain comments and additions to the arguments by other writers, we may pass on to a paper by Dr. R. Broom, published in the _Proceedings_ of the Linnean Society of New South Wales for April 1898, and entitled “On the Affinities and Habits of _Thylacoleo_.”

In this the author admits that the animal in question, as suggested by Owen in his second paper, and more fully determined by Flower, was undoubtedly a diprotodont, and that it was nearly allied to the modern phalangers. With the latter it is indeed closely connected by the recently discovered extinct _Burramys_, which differs from the existing members of that group by the large size of the secant premolar.

After discussing numerous points in connection with the problem, Dr. Broom states that those who believe _Thylacoleo_ to have been carnivorous, “evidently consider that the molars have been reduced through their functions being taken up by the large premolars. But could the large premolars take up the molar function—could they grind? Even those who favour the idea of _Thylacoleo_ being a vegetable-feeder, admit that the premolars were cutting teeth, and the difficulty of imagining a herbivorous animal without grinders is got over by supposing that its food was of a soft or succulent nature.”

But for the creature to have lived on succulent roots and bulbs, the vegetation of that part of Australia where it lived must, urges Dr. Broom, have been quite different from what it is at the present day; and we have no justification for assuming any such change to have taken place. Moreover, an animal that could only slice, and not grind up, vegetable food, could apparently subsist only on ripe fruit, and such is to be met with in Australia only at one season of the year, when, owing to the abundance of frugivorous mammals, little, if any, is allowed to fall to the ground.

“It is probably however,” adds Dr. Broom, “unnecessary to discuss further what food _Thylacoleo_ could possibly have obtained, when we have, as I hold with Owen, the most satisfactory proof from its anatomical structure as to what food it did obtain. It must be admitted that _Thylacoleo_ had enormous temporal muscles, and it is perfectly certain that such muscles would not have been developed unless the animal required them. For what could such powerful muscles be required? Most certainly not for slicing fruits or succulent roots and bulbs, nor would they be required even for the slicing of fleshy fibres. Temporal muscles are chiefly used apparently for closing the jaws more or less forcibly from the open position, while for the more complicated movements of mastication it is the masseter and pterygoid muscles that are chiefly used. Hence in all carnivorous animals the temporals are largely developed and the masseters more feebly, because the killing process requires a very forcible closing of the jaws, and the work to be done by the premolars and molars is comparatively little. In herbivorous animals the conditions are reversed. The jaws are here rarely required to be opened widely or to be closed with any great force, while a very large amount of grinding work has to be done; hence the temporals are rarely much larger than the masseters, and often very much smaller. When we look at _Thylacoleo_, we find not only the enormous temporals and only moderate masseters, but everything else about the skull seems to be built on carnivorous lines. Owen has shown the wonderful similarity which exists between the molar machinery in _Thylacoleo_ and the lion, and it is hard to conceive as possible any other cause giving rise to such a specialisation in _Thylacoleo_ than that which led to a similar specialisation in the cat tribe. Another most striking feature is to be seen in the condition of the incisors. Leaving out of consideration the mode of implantation and structure of the teeth—both confirmatory of the carnivorous hypothesis—there is one point which appears to me absolutely conclusive on the subject. Unless Owen’s figures are altogether unreliable, the lower incisors are quite unlike those of the herbivorous diprotodonts. In such typical forms as the wombat, the koala, the kangaroo, and the phalanger, though there are different modifications of the arrangement, we have the lower incisors meeting the upper, and forming with them an instrument for biting through a moderately tough, fibrous tissue, and even in the very small diprotodonts, so far as I am aware, the lower incisors always meet and work against the upper. But in _Thylacoleo_ we have powerful pointed incisors which do not meet, but overlap. Though technically incisors, they are not intended to incise, but to pierce and tear. Such powerful pointed and overlapping teeth, though easily explained on the theory that they were intended to kill and tear animal prey, were never surely provided merely to pierce succulent vegetables or ripe fruit. It might of course be argued that the incisors were used as weapons of defence, as apparently are the canines in the baboon; but against this idea is the objection that the incisors were put to some use which wore them down and blunted them more rapidly than would be the case if they were chiefly used on the rare occasions when the animal had to defend itself; and furthermore, were such the case, the temporals would not require to be greatly developed.

“There is thus, in my opinion, no other conclusion tenable than that _Thylacoleo_ was a purely carnivorous animal, and one which would be quite able to, and probably did, kill animals as large as or larger than itself.”

This opinion as to the carnivorous habits of _Thylacoleo_ is approved by Mr. B. A. Bensley, who has specially studied the Australian marsupials in a memoir recently published in the _Transactions_ of the Linnean Society of London.

If it be correct, it reduces the net result of Flower’s investigations on this subject to a fuller realisation of the diprotodont affinities of the animal under consideration.

In the latter part of 1868, Mr. Flower, as he was then styled, communicated to the Zoological Society a most important paper entitled, “On the Value of the Characters of the Base of the Cranium in the Classification of the Order Carnivora,” which was published in the first part of the Society’s _Proceedings_ for the following year. Working on the lines suggested twenty years previously by Mr. H. N. Turner, who had pointed out the importance of certain peculiarities of the base of the skull in the Mammalia, and especially demonstrated their constancy in the different groups of the Carnivora, Flower felt himself justified in dividing, on these characters, the existing terrestrial representatives of that order into three groups. These were—1st, the Æluroidea, comprising the cats (_Felidæ_), the fossa (_Cryptoproctidæ_), civets and mongooses (_Viverridæ_), the aard-wolf (_Proteleidæ_), and hyænas (_Hyænidæ_); 2nd, the Cynoidea, including only the dogs, wolves, and foxes; and 3rd, the Arctoidea, embracing the bears (_Ursidæ_), the raccoons and pandas (_Procyonidæ_ and _Æluridæ_), and the weasels, badgers, otters, etc. (_Mustelidæ_).

One result of this classification from cranial characteristics was to determine definitely the position of the American cacomistle (_Bassaris_ or _Bassariscus_), which had been previously uncertain. The genus, as might have been expected from distributional considerations, turned out to belong to the raccoon family (_Procyonidæ_).

As regards the relationship of the three main groups, subsequent palæontological discoveries have fully confirmed Flower’s view that the _Canidæ_ (Cynoidea) occupy a central, or perhaps rather a basal, position. Palæontology has, however, also shown that the bears (_Ursidæ_) are a direct offshoot from the _Canidæ_, and accordingly that, if extinct forms be taken into consideration, there is no justification for the separation of the two families into distinct primary groups (Arctoidea and Cynoidea). On the other hand, fossil forms from the Lower Tertiaries of France and of North America seem to demonstrate the existence of a complete gradation between the primitive dogs (_Canidæ_) and the ancestral civets (_Viverridæ_), thus breaking up the distinction between the Cynoidea and the Æluroidea. Nor is this all, for according to the French palæontologists, there exists a transition between the primitive civets and the early weasels (_Mustelidæ_); which, with what has been already stated in connection with the bears, indicates that the Arctoidea is a more or less artificial group, the members of which have come to resemble one another to a certain degree in regard to the characters of the base of the skull, owing to “parallelism.” In this connection it is somewhat curious to note that a certain resemblance, which had been pointed out by Turner as existing between the mongooses or ichneumons (_Viverridæ_) and the weasels, was regarded by Flower as of no importance. Finally, it is by no means improbable that the cats (_Felidæ_) have no near kinship with the civets, but may be directly sprung from more primitive Carnivora.

It is thus evident that Flower’s proposed triple division of the Carnivora is not altogether in accord with palæontological, or phylogenetic, evidence. An amendment is to merge the Cynoidea in the Arctoidea, and thus retain only two groups. The observations recorded in the paper have a high permanent value, in respect to the structure of the carnivorous skull.

Another paper by Flower appeared in the Zoological Society’s _Proceedings_ for 1869, dealing with the anatomy of the soft parts of that remarkable animal, the African aard-wolf (_Proteles cristatus_). Although the skeleton had been previously described, no information had hitherto been available with regard to the viscera. In the paper discussed in the foregoing paragraphs Flower, from the external characters, coupled with those of the dentition and skeleton, had regarded the creature as the representative of a distinct family, intermediate in some respects between the _Hyænidæ_ and the _Viverridæ_. The result of the examination of the viscera was in the main to support this conclusion, although it showed that the _Proteleidæ_ are more closely allied to the _Hyænidæ_ than the author had previously believed to be the case. The aard-wolf may, indeed, be regarded as a kind of small and degraded hyæna, with an almost rudimentary type of dentition, suitable to the soft substances on which it feeds.

Passing on to the year 1870, we have to note the appearance of two separate works bearing Flower’s name. The first of these was the _Introductory Lectures to the Course of Comparative Anatomy_, delivered at the Royal College of Surgeons in that year. Far more important was the issue of the first edition of that invaluable text-book, _An Introduction to the Osteology of the Mammalia_. Since, however, mention of this work had been already made in an earlier chapter, it need not be further alluded to in this place.

During the same year, exclusive of those on the Cetacea, several papers were published by Flower in various scientific serials. Among these, bare mention must suffice for one, “On the Connexion of the Hyoid Arch with the Cranium,” which appeared in the twentieth volume of the _Report_ of the British Association. More important is the article “On the Correspondence between the parts composing the Shoulder and the Pelvic Girdle of the Mammalia.” In this the author pointed out that although the homology between the scapula in the shoulder-girdle and the ilium in the pelvis had long been admitted by naturalists, yet much misconception existed with regard to the exact correspondence between the respective surfaces and borders of these bones; and he then proceeded to define and describe these correspondences in considerable detail. The names then assigned by Flower to the component surfaces and borders of the bones in question have ever since been generally adapted by naturalists. Observations were also recorded with regard to the homology between the coracoid bone and the ischium. A second paper in the same journal for 1870 dealt with the carpus of the dog; while in 1873 he published in this medium a note on the same part of the skeleton in the sloths.

Reverting once more to the _Proceedings_ of the Zoological Society, in which the bulk of his contributions to the anatomy of mammals was published, we find a paper by Flower in the volume for 1870 on the anatomy of the Himalayan panda (_Ælurus fulgens_.)

The specimen on which the paper was based was the first example of this remarkable animal which had ever been dissected; and the brain and viscera were described at considerable length. The result of the dissection was to confirm the author’s previous opinion—based on the external characters and skeleton—as to the near affinity of _Ælurus_ to the American _Procyonidæ_; and it was left somewhat an open question, whether it should be included in that group, or regarded as the representative of a family (_Æluridæ_) by itself. In after years Mr. W. T. Blanford adopted the former view. In the following year (1871) Flower contributed a note to the _Proceedings_, recording the occurrence of a specimen of the ringed seal (_Phoca hispida_) on the Norfolk coast in 1846; and he also wrote a paper in the same volume on the skeleton of one of the cassowaries. The somewhat remarkable fact that the two-spotted palm-civet (_Nandinia binotata_) differs from the other genera of the same group by the absence of a blind appendage, or cæcum, to the intestine, was recorded by Flower in the same serial for 1872.

Of much more importance than either of the foregoing were two contributions to mammalian anatomy made by Sir William during the year last mentioned. The one, which appeared in the _Medical Times and Gazette_, was the report of “Lectures on the Comparative Anatomy of the Organs of Digestion in the Mammalia, delivered at the Royal College of Surgeons in February and March, 1872.” In this article, which is well illustrated, will be found descriptions of the various forms assumed by the stomach in a large number of the ordinal and family groups; especial attention being directed to the remarkable complexity of that organ in the porpoise. The other, which was published in _Nature_, and in abstract in the _Report_ of the British Association, dealt with the arrangement and nomenclature of the lobes of the mammalian liver. It is, perhaps, one of the most valuable of the author’s contributions to visceral anatomy; and introduced order and precision where confusion had previously reigned. The names then given to the different lobes of the liver have been very generally adopted in zoological and anatomical literature.

In 1873 Flower delivered before the Royal Institution a lecture on palæontological evidence of gradual modification of animal forms, which is published in the _Proceedings_ of that body for the same year. In this he touched on the important evidence afforded by the discoveries which had then been recently made in North America in favour of the derivation of one animal form from another, directing particular attention to the case for the evolution of the horse. Another paper on the same subject appears in the _British Medical Journal_ for 1874; while, as noticed below, Sir William again lectured on palæontological evolution in 1876.

The year 1874 was noteworthy, so far as palæontology is concerned, by the appearance in the _Philosophical Transactions_ of the Royal Society of a paper by Flower on part of a remarkable mammalian skull from Patagonia, described under the name of _Homalodontotherium cunninghami_. In justice to the author, it should be said that he was not responsible for the undue length of the generic name, which had been bestowed by his friend Huxley four years previously in the Geological Society’s _Journal_, and which Flower was therefore compelled to employ. It refers to the fact that the jaws of the new animal are remarkable for the even and unbroken wall formed by the teeth, which show no enlarged tusks. At the time the geological age of this interesting fossil was quite unknown; but it formed the forerunner of the marvellous discoveries of the remains of fossil mammals of middle tertiary age in Patagonia, which have been made of late years, and have done so much to increase our knowledge of the past life and history of the South American Continent.

Of minor interest is a paper by the then Hunterian Professor in the _Quarterly Journal_ of the Geological Society on a much rolled and battered skull from the so-called Red Crag of Suffolk, which the author referred to a species of that extinct genus of sea-cows (Sirenia) known as _Halitherium_. Such interest as the specimen possessed was due to its affording the first evidence of the occurrence of remains of that genus in Britain. Another paper, it may be mentioned, was published by Flower in the same journal for 1877, in which another well-known extinct continental genus of mammals was added to the fauna of the Red Crag of East Anglia. The paper described two molar teeth, in the York Museum, from the deposit in question, evidently referable to the large bear-like animal known as _Hyænarctus_, of which the first remains had been described many years previously from the Siwalik Hills of North-Eastern India. As the mention of this paper has broken the chronological order of treatment, it may be added that in 1876 Flower published another paper, this time in the Zoological Society’s _Proceedings_, on a mammalian skull from the Red Crag. The specimen referred to in this communication was provisionally assigned to Cuvier’s genus _Xiphodon_, and was believed to have been originally washed out from a formation much older than the Red Crag, and reburied in the latter.

Next on our list comes a paper on the anatomy of the musk-deer (_Moschus moschiferus_), contributed to the serial last cited for 1875, in which the author points out how widely this animal differs from the more typical deer, and shows that it cannot even claim a near relationship with the Chinese water-deer, despite the fact that in both species the males are devoid of antlers, and are armed with long sabre-like tusks in the upper jaw. In several respects—notably the presence of a gall-bladder to the liver—the musk-deer is indeed nearer to the hollow-horned ruminants (Bovidæ), than to the other members of the deer tribe (Cervidæ).

In 1876 Professor Flower delivered before the Royal Institution an extremely interesting lecture on the extinct mammals of North America, which at that time were in course of being made known to the scientific world by the writings of Professors Marsh and Cope. In the course of this lecture Flower alluded at considerable length to the ancestry of the horse—then a comparatively new subject—and also discussed the structure and affinities of those gigantic many-horned mammals commonly known as Dinocerata. In concluding, the lecturer observed that the work accomplished in America taught us—“First, that the living world around us at the present moment bears but an exceedingly small proportion to the whole series of animal and vegetable forms which have existed in past ages. Secondly, that, notwithstanding all that has been said, and most justly said, of the necessary imperfection of the geological record, we may hope that there is still so much preserved that the study of the course of events which have led up to the present condition of life on the globe, may have a great future before it.”

The subsequent discoveries of fossil mammalian remains in such enormous quantities in Patagonia, and still later in the Libyan desert, have rendered this utterance almost prophetic.

During the same year (1876) appeared, in the _Philosophical Transactions_, a notice by Flower of the seals and cetaceans obtained during the _Transit of Venus_ expeditions of 1874 and 1875. The year 1876 likewise witnessed the publication, in the _Proceedings_ of the Zoological Society, of an article on the skulls of the various existing species of rhinoceroses, in which it was shown that the number of such species had been altogether unjustifiably exaggerated by the late Dr. J. E. Gray and other writers, and that in all probability there were really not more than five. Certain characters connected with the postero-lateral region of the skull were also described, which served to divide these species into groups. A further contribution to our knowledge of the skulls of the rhinoceroses was made by Flower in 1878, when he described, in the same journal, the skull of an Indian specimen, which it was thought might be the _Rhinoceros lasiotis_ of Dr. Sclater—now known to be (as then suggested) merely a local race of the two-horned _R. sumatrensis_.

Between the years 1880 and 1883 several papers on mammalian zoology were published by Flower in the _Proceedings_ of the Zoological Society and elsewhere, none of which can be regarded as of first-rate importance. The first of these (_P.Z.S._ 1880) dealt with the internal anatomy of that rare mammal, the bush-dog (_Speothus_, or _Icticyon_, _venaticus_), of Guiana, which had never previously been described. The author regarded this animal as a specialised member of the Canidæ, showing some signs of affinity with the wild dogs (_Cyon_) of Asia. In 1880 the museum of the Royal College of Surgeons received a very large skull of the elephant-seal or sea-elephant (_Macrorhinus leoninus_); and this induced Flower to draw up some notes on that enormous creature, which appeared in the above-named journal for 1881. The author described it as “an animal which, notwithstanding its former abundance and wide distribution, and its great zoological interest, is still very imperfectly known anatomically, and very poorly represented in collections.” Fortunately, since that date—mainly owing to the energy and liberality of Mr. Rothschild—specimens of the skin and skeleton of this huge seal have been secured for our museums before it was too late. In the same volume Flower drew attention to the evidence showing that the sea-cow, or manati, of which a pair were living at the time in the Brighton Aquarium, occasionally, or periodically, comes ashore for the purpose of grazing. In the same year appeared an article from his pen in the _British Medical Journal_ on the anatomy of the Cetacea and Edentata; while in 1882 the question of the mutual relationships of the mammals commonly included in the latter order (such as sloths, ant-eaters, armadillos, pangolins, and aard-varks) were discussed by him in the _Proceedings_ of the Zoological Society.

The trend of the paper last mentioned, as well as that of some of his other communications published shortly before, indicates that about this time, instead of restricting his attention more or less entirely to their anatomy, Flower was much occupied with the subject of the classification of the Mammalia. And the reason is not far to seek, for he had undertaken not only the volume of the “Catalogue of Osteological Specimens in the Museum of the Royal College of Surgeons,” dealing with mammals other than man, but he had likewise engaged (in co-operation with the late Dr. Dobson) to write the article “Mammalia” for the ninth edition of the _Encyclopædia Britannica_. With the view apparently of clearing the way for these two important contributions to zoology, he published during the early part of 1883 in the Zoological Society’s _Proceedings_ a paper on the “Arrangement of the Orders and Families of Mammalia.”

To discuss this important paper in detail on the present occasion is quite unnecessary; and it will suffice to state that it has formed the basis on which all modern classifications of the group are framed. Indeed it has been accepted by most writers with little or no modification. In this scheme it was proposed to divide mammals into three primary groups, or sub-classes, namely, Prototheria, or Ornithodelphia, as represented only by the egg-laying group; Metatheria or Didelphia, including the pouched group, or marsupials; and Eutheria or Monodelphia, comprising the whole of the remaining or placental groups. Of late years, owing to the discovery of unexpected relationships between placentals and marsupials, it has been proposed to recognise only two sub-classes of mammals: the Eutheria, comprising the two groups last mentioned, and the Prototheria, or monotremes. The scheme chiefly differed from the one proposed some years earlier by Huxley in the inclusion of the Hyracoidea (klipdass) and Proboscidea (elephants) as sub-orders of the Ungulata, instead of their forming separate orders by themselves. In this instance Flower ranked the Artiodactyla, Perissodactyla, Hyracoidea, and Proboscidea as equivalent sub-orders of Ungulata, but later on he brigaded the two former together as Ungulata Vera, and the two latter as Subungulata.

The above scheme was employed by Flower in the article “Mammalia,” written by him for the ninth edition of the _Encyclopædia Britannica_, the volume containing which appeared in 1883. This article, with others by himself and other authors, formed, as will be noticed later on, the basis of the _Study of Mammals_ published in 1891. Among other articles contributed by Flower to the _Encyclopædia_ were those on the Horse, Kangaroo, Lemur, Lion, Mastodon, Megatherium, Otter, Platypus, Rhinoceros, Seal, Swine, Tapir, Whale, and Zebra.

The aforesaid scheme of classification was likewise used in the second part of the “Catalogue of Osteological Specimens in the Museum of the Royal College of Surgeons,” which was written with the assistance of Dr. Garson, and appeared in 1884. Since this valuable work has been already noticed at some length in the chapter devoted to Flower’s official connection with the College of Surgeons, it need not be further referred to in this place, except that the writer may again take the opportunity of expressing his regret that the views on nomenclature there enunciated have not met with acceptance among the modern school of naturalists.

At the “Jubilee” meeting of the Zoological Society, held in June 1887, Flower, as President, read an address on the “Progress of Zoological Science” during the reign of Queen Victoria, which appeared in the _Report_ of the Council of that year, and to which reference has been made in an earlier chapter.

About this time the Natural History Museum received a series of antlers shed year by year by one particular red-deer stag, together with the complete skull and antlers of the same animal; and this gift induced Flower to deliver in December 1887 a lecture on “Horns and Antlers” before the Middlesex Natural History Society, which is printed, with a plate of the aforesaid series of red-deer antlers, in a somewhat abbreviated form, in the _Transactions_ of that Society.

If we except a few on Cetacea, noticed in the next chapter, Sir William’s contributions to the Zoological Society’s _Proceedings_ after 1883 were not numerous or of much importance. In 1884 he contributed, however, remarks on the so-called white elephant from Burma, then exhibited in the Society’s Menagerie; and in the same year he also wrote on the young dentition of the capybara. In 1887 he discussed the generic position and relationships of the pigmy hippopotamus of Liberia. The acquisition in the following year by the Natural History Museum of specimens of that breed of Japanese fowls remarkable for the excessive elongation of the tail-feathers of the cocks, led to a note on that subject in the _Proceedings_ for the same year. This paper, it may be incidentally mentioned, is noteworthy, on account of the evidence it affords that Sir William did not regard the variations displayed by domesticated animals as in any way unworthy the notice of the naturalist; while the next shows that monstrosities or abnormalities—at all events to a certain extent—are also worthy of recognition. The note incidentally alluded to in the last sentence appeared in 1889, and dealt with an African rhinoceros head, showing three horns. Finally, in 1890, Sir William exhibited and commented upon a photograph of the nesting-hole of a hornbill, showing the female “walled up” with mud.

The next year (1891) saw the publication of _An Introduction to the Study of Mammals, Living and Extinct_, written, as already said, in collaboration with the present writer, and embodying the whole of Flower’s contributions to the _Encyclopædia Britannica_, together with certain articles by other authors from the same work, and such new material as was necessary in order to weave these _disjecta membra_ into one connected and harmonious whole.

In the same year was also published, in the _Modern Science Series_, Sir William’s admirable little volume on _The Horse_, which was likewise largely based on his _Encyclopædia_ articles. In this work Flower dwelt particularly on the vestiges exhibited by the modern horse of its descent from more generalised ancestors; and he was successful in demonstrating that the structure known to veterinarians as the “ergot,” represents one of the foot-pads of the earlier forms.

Undoubtedly the most important elements in the foregoing tale of work are those relating to the mammalian (and especially the marsupial) brain, and the marsupial dentition. And if Flower had accomplished nothing more than this, he would have been entitled to gratitude of his successors. But, as we shall immediately see, all the above formed but a portion of his zoological labours.