Chapter XV

. Lyell laid down the principle that we are to interpret occurrences in the past in the terms of what is occurring in the present. He demonstrated that observations upon the present show that the surface of the earth is undergoing gradually slow changes through the action of various agents, and he pointed out that we must view the occurrences in the past in the light of occurrences in the present. Once this was applied to animal forms it became evident that the observations upon animals and plants in the present must be applied to the life of the fossil series.

These ideas, then, paved the way for the conception of changes in nature as being one continuous series.

H. Spencer.--In 1852 came the publication of Herbert Spencer in the _Leader_, in which he came very near anticipating the doctrine of natural selection. He advanced the developmental hypothesis, saying that even if its supporters could "merely show that the production of species by the process of modification is conceivable, they would be in a better position than their opponents. But they can do much more than this; they can show that the process of modification has affected and is affecting great changes in all organisms subject to modifying influences.... They can show that any existing species, animal or vegetable, when placed under conditions different from its previous ones, immediately begins to undergo certain changes of structure fitting it for the new conditions. They can show that in successive generations these changes continue, until ultimately the new conditions become the natural ones. They can show that in cultivated plants and domesticated animals, and in the several races of men, these changes have uniformly taken place. They can show that the degrees of difference so produced are often, as in dogs, greater than those on which distinctions of species are in other cases founded. They can show that it is a matter of dispute whether some of these modified forms _are_ varieties or modified species. And thus they can show that throughout all organic nature there is at work a modifying influence of the kind they assign as the cause of these specific differences; an influence which, though slow in its action, does in time, if the circumstances demand it, produce marked changes; an influence which, to all appearance, would produce in the millions of years, and under the great varieties of conditions which geological records imply, any amount of change."

"It is impossible," says Marshall, "to depict better than this the condition prior to Darwin. In this essay there is full recognition of the fact of transition, and of its being due to natural influences or causes, acting now and at all times. Yet it remained comparatively unnoticed, because Spencer, like his contemporaries and predecessors, while advocating evolution, was unable to state explicitly what these causes were."

Darwin and Wallace.--In 1858 we come to the crowning event in the rise of evolutionary thought, when Alfred Russel Wallace sent a communication to Mr. Darwin, begging him to look it over and give him his opinion of it. Darwin, who had been working upon his theory for more than twenty years, patiently gathering facts and testing the same by experiment, was greatly surprised to find that Mr. Wallace had independently hit upon the same principle of explaining the formation of species. In his generosity, he was at first disposed to withdraw from the field and publish the essay of Wallace without saying anything about his own work. He decided, however, to abide by the decision of two of his friends, to whom he had submitted the matter, and the result was that the paper of Wallace, accompanied by earlier communications of Darwin, were laid before the Linnæan Society of London. This was such an important event in the history of science that its consideration is extended by quoting the following letter:

"London, June 30th, 1858.

"My Dear Sir: The accompanying papers, which we have the honor of communicating to the Linnæan Society, and which all relate to the same subject; _viz_., the laws which affect the production of varieties, races, and species, contain the results of the investigations of two indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace.

"These gentlemen having, independently and unknown to one another, conceived the same very ingenious theory to account for the appearance and perpetuation of varieties and of specific forms on our planet, may both fairly claim the merit of being original thinkers in this important line of inquiry; but neither of them having published his views, though Mr. Darwin has for many years past been repeatedly urged by us to do so, and both authors having now unreservedly placed their papers in our hands, we think it would best promote the interests of science that a selection from them should be laid before the Linnæan Society.

"Taken in the order of their dates, they consist of:

"1. Extracts from a MS. work on species, by Mr. Darwin, which was sketched in 1839 and copied in 1844, when the copy was read by Dr. Hooker, and its contents afterward communicated to Sir Charles Lyell. The first part is devoted to _The Variation of Organic Beings under Domestication and in their Natural State_; and the second chapter of that part, from which we propose to read to the Society the extracts referred to, is headed _On the Variation of Organic Beings in a State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and True Species_.

"2. An abstract of a private letter addressed to Professor Asa Gray, of Boston, U.S., in October, 1857, by Mr. Darwin, in which he repeats his views, and which shows that these remained unaltered from 1839 to 1857.

"3. An essay by Mr. Wallace, entitled _On the Tendency of Varieties to Depart Indefinitely from the Original Type_. This was written at Ternate in February, 1858, for the perusal of his friend and correspondent, Mr. Darwin, and sent to him with the expressed wish that it should be forwarded to Sir Charles Lyell, if Mr. Darwin thought it sufficiently novel and interesting. So highly did Mr. Darwin appreciate the value of the views therein set forth that he proposed, in a letter to Sir Charles Lyell, to obtain Mr. Wallace's consent to allow the essay to be published as soon as possible. Of this step we highly approved, provided Mr. Darwin did not withhold from the public, as he was strongly inclined to do (in favor of Mr. Wallace), the memoir which he had himself written on the same subject, and which, as before stated, one of us had perused in 1844, and the contents of which we had both of us been privy to for many years.

"On representing this to Mr. Darwin, he gave us permission to make what use we thought proper of his memoir, etc.; and in adopting our present course, of presenting it to the Linnæan Society, we have explained to him that we are not solely considering the relative claims to priority of himself and his friend, but the interests of science generally; for we feel it to be desirable that views founded on a wide deduction from facts, and matured by years of reflecting, should constitute at once a goal from which others may start; and that, while the scientific world is waiting for the appearance of Mr. Darwin's complete work, some of the leading results of his labours, as well as those of his able correspondent, should together be laid before the public.

"We have the honour to be yours very obediently,

Charles Lyell,

Jos. D. Hooker."

Personality of Darwin.--The personality of Darwin is extremely interesting. Of his numerous portraits, the one shown in Fig. 119 is less commonly known than those showing him with a beard and a much furrowed forehead. This portrait represents him in middle life, about the time of the publication of his _Origin of Species_. It shows a rather typical British face, of marked individuality. Steadiness, sincerity, and urbanity are all depicted here. His bluish-gray eyes were overshadowed by a projecting ridge and very prominent, bushy eyebrows that make his portrait, once seen, easily recognized thereafter. In the full-length portraits representing him seated, every line in his body shows the quiet, philosophical temper for which he was notable. An intimate account of his life is contained in the _Life and Letters of Charles Darwin_ (1887) and in _More Letters of Darwin_ (1903), both of which are illustrated by portraits and other pictures. The books about Darwin and his work are numerous, but the reader is referred in particular to the two mentioned as giving the best conception of the great naturalist and of his personal characteristics.

[Illustration: Fig. 119.--Charles Darwin, 1809-1882.]

He is described as being about six feet high, but with a stoop of the shoulders which diminished his apparent height; "of active habits, but with no natural grace or neatness of movement." "In manner he was bright, animated, and cheerful; a delightfully considerate host, a man of never-failing courtesy, leading him to reply at length to letters from anybody, and sometimes of a most foolish kind."

His Home Life.--"Darwin was a man greatly loved and respected by all who knew him. There was a peculiar charm about his manner, a constant deference to others, and a faculty for seeing the best side of everything and everybody."

He was most affectionate and considerate at home. The picture of Darwin's life with his children gives a glimpse of the tenderness and deep affection of his nature, and the reverent regard with which he was held in the family circle is very touching. One of his daughters writes: "My first remembrances of my father are of the delights of his playing with us. He was passionately attached to his own children, although he was not an indiscriminate child-lover. To all of us he was the most delightful playfellow, and the most perfect sympathizer. Indeed, it is impossible adequately to describe how delightful a relation his was to his family, whether as children or in their later life.

"It is a proof of the terms on which we were, and also of how much he was valued as a playfellow, that one of his sons, when about four years old, tried to bribe him with a sixpence to come and play in working hours. We all knew the sacredness of working time, but that any one should resist sixpence seemed an impossibility."

Method of Work.--Darwin's life, as might be inferred from the enduring quality of his researches, shows an unswerving purpose. His theory was not the result of a sudden flash of insight, nor was it struck out in the heat of inspiration, but was the product of almost unexampled industry and conscientious endeavor in the face of unfavorable circumstances. Although strikingly original and independent as a thinker, he was slow to arrive at conclusions, examining with the most minute and scrupulous care the ground for every conclusion. "One quality of mind that seemed to be of especial advantage in leading him to make discoveries was the habit of never letting exceptions pass unnoticed." He enjoyed experimenting much more than work which only entailed reasoning. Of course, he was a great reader, but for books as books he had no respect, often cutting large ones in two in order to make them easier to hold while in use.

Darwin's Early Life.--Charles Darwin was born in 1809 at Shrewsbury, England, of distinguished ancestry, his grandfather being the famous Dr. Erasmus Darwin, the founder, as we have seen, of a theory of evolution. In his youth he gave no indication of future greatness. He was sent to Edinburgh to study medicine, but left there after two sessions, at the suggestion of his father, to study for the Church. He then went to the University of Cambridge, where he remained three years, listening to "incredibly dull lectures." After taking his baccalaureate degree, came the event which proved, as Darwin says, "the turning-point of my life." This was his appointment as naturalist on the surveying expedition about to be entered upon by the ship _Beagle_. In Cambridge he had manifested an interest in scientific study, and had been encouraged by Professor Henslow, to whom he was also indebted for the recommendation to the post on the _Beagle_. An amusing circumstance connected with his appointment is that he was nearly rejected by Captain Fitz-Roy, who doubted "whether a man with such a shaped nose could possess sufficient energy and determination for the voyage."

Voyage of the Beagle.--The voyage of the _Beagle_ extended over five years (1831-1836), mainly along the west coast of South America. It was on this voyage that Darwin acquired the habit of constant industry. He had also opportunity to take long trips on shore, engaged in observation and in making extensive collections. He observed nature in the field under exceptional circumstances. As he traveled he noted fossil forms in rocks as well as the living forms in field and forest. He observed the correspondence in type between certain extinct forms and recent animals in South America. He noticed in the Galapagos Islands a fauna similar in general characteristics to that of the mainland, five or six hundred miles distant, and yet totally different as to species. Moreover, certain species were found to be confined to

## particular islands. These observations awakened in his mind, a mind

naturally given to inquiring into the causes of things, questions that led to the formulation of his theory. It was not, however, until 1837 that he commenced his first note-book for containing his observations upon the transmutations of animals. He started as a firm believer in the fixity of species, and spent several years collecting and considering data before he changed his views.

At Downs.--On his return to England, after spending some time in London, he purchased a country-place at Downs, and, as his inheritance made it possible, he devoted himself entirely to his researches.

But, as is well known, he found in his illness a great obstacle to steady work. He had been a vigorous youth and young man, fond of outdoor sports, as fishing, shooting, and the like. After returning from his long voyage, he was affected by a form of constant illness, involving a giddiness in the head, and "for nearly forty years he never knew one day of the health of an ordinary man, and thus his life was one long struggle against the weariness and strain of sickness." Gould in his _Biographical Clinics_ attributes his illness to eye-strain.

"Under such conditions absolute regularity of routine was essential, and the day's work was carefully planned out. At his best, he had three periods of work: from 8.00 to 9.30; from 10.30 to 12.15; and from 4.30 to 6.00, each period being under two hours' duration."

The patient thoroughness of his experimental work and of his observation is shown by the fact that he did not publish his book on the _Origin of Species_ until he had worked on his theory twenty-two years. The circumstances that led to his publishing it when he did have already been indicated.

Parallelism in the Thought of Darwin and Wallace.--No one can read the letters of Darwin and Wallace explaining how they arrived at their idea of natural selection without marveling at the remarkable parallelism in the thought of the two. It is a noteworthy circumstance that the idea of natural selection came to both by the reading of the same book, _Malthus on Population_.

Darwin's statement of how he arrived at the conception of natural selection is as follows: "In October, 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement _Malthus on Population_, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observations of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved and unfavourable ones to be destroyed. _The result of this would be the formation of new species._ Here then I had at last got a theory by which to work, but I was so anxious to avoid prejudice that I determined not for some time to write even the briefest sketch of it. In June, 1842, I first allowed myself the satisfaction of writing a very brief abstract of my theory in pencil, in thirty-five pages, and this was enlarged during the summer of 1844 into one of 230 pages."

[Illustration: Fig. 120.--Alfred Russel Wallace, Born 1823.]

And Wallace gives this account: "In February, 1858, I was suffering from a rather severe attack of intermittent fever at Ternate, in the Moluccas; and one day, while lying on my bed during the cold fit, wrapped in blankets, though the thermometer was at 88° Fahr., the problem again presented itself to me, and something led me to think of the 'positive checks' described by Malthus in his _Essay on Population_, a work I had read several years before, and which had made a deep and permanent impression on my mind. These checks--war, disease, famine, and the like--must, it occurred to me, act on animals as well as man. Then I thought of the enormously rapid multiplication of animals, causing these checks to be much more effective in them than in the case of man; and while pondering vaguely on this fact, there suddenly flashed upon me the _idea_ of the survival of the fittest--that the individuals removed by these checks must be on the whole inferior to those that survived. In the two hours that elapsed before my ague fit was over, I had thought out almost the whole of the theory; and the same evening I sketched the draught of my paper, and in the two succeeding evenings wrote it out in full, and sent it by the next post to Mr. Darwin."

It thus appears that the announcement of the Darwin-Wallace theory of natural selection was made in 1858, and in the following year was published the book, the famous _Origin of Species_, upon which Darwin had been working when he received Mr. Wallace's essay. Darwin spoke of this work as an outline, a sort of introduction to other works that were in the course of preparation. His subsequent works upon _Animals and Plants under Domestication_, _The Descent of Man_, etc., etc., expanded his theory, but none of them effected so much stir in the intellectual world as the _Origin of Species_.

This skeleton outline should be filled out by reading _Darwin's Life and Letters_, by his son, and the complete papers of Darwin and Wallace, as originally published in the _Journal of the Linnæan Society_. The original papers are reproduced in the _Popular Science Monthly_ for November, 1901.

Wallace was born in 1823, and is still living. He shares with Darwin the credit of propounding the theory of natural selection, and he is notable also for the publication of important books, as the _Malay Archipelago_, _The Geographical Distribution of Animals_, _The Wonderful Century_, etc.

The Spread of the Doctrine of Organic Evolution. Huxley.--Darwin was of a quiet habit, not aggressive in the defense of his views. His theory provoked so much opposition that it needed some defenders of the pugnacious type. In England such a man was found in Thomas Henry Huxley (1825-1895). He was one of the greatest popular exponents of science of the nineteenth century; a man of most thorough and exact scholarship, with a keen, analytical mind that went directly to the center of questions under consideration, and powers as a writer that gave him a wide circle of readers. He was magnificently sincere in his fight for the prevalence of intellectual honesty. Doubtless he will be longer remembered for this service than for anything else.

[Illustration: Fig. 121.--Thomas Henry Huxley, 1825-1895.]

He defended the doctrine of evolution, not only against oratorical attacks like that of Bishop Wilberforce, but against well-considered arguments and more worthy opponents. He advanced the standing of the theory in a less direct way by urging the pursuit of scientific studies by high-school and university students, and by bringing science closer to the people. He was a pioneer in the laboratory teaching of biology, and his _Manual_ has been, ever since its publication in 1874, the inspiration and the model for writers of directions for practical work in that field.

It is not so generally known that he was also a great investigator, producing a large amount of purely technical researches. After his death a memorial edition of his scientific memoirs was published in four large quarto volumes. The extent of his scientific output when thus assembled was a surprise to many of his co-workers in the field of science. His other writings of a more general character have been collected in fourteen quarto volumes. Some of the essays in this collection are models of clear and vigorous English style. Mr. Huxley did an astonishing amount of scientific work, especially in morphology and palæontology. Those who have been privileged to look over his manuscripts and unpublished drawings in his old room at South Kensington could not fail to have been impressed, not only with the extent, but also with the accuracy of his work. Taking Johannes Müller as his exemplar, he investigated animal organisms with a completeness and an exactness that have rarely been equaled.

An intimate account of his life will be found in _The Life and Letters of Thomas Henry Huxley_, by his son.

Haeckel.--Ernst Haeckel, of Jena, born in 1834 (Fig. 122), was one of the earliest in Germany to take up the defense of Darwin's hypothesis. As early as 1866 he applied the doctrine of evolution to all organisms in his _Generelle Morphologie_. This work, which has been long out of print, represents his best contribution to evolutionary thought. He has written widely for general readers, and although his writings are popularly believed to represent the best scientific thought on the matter, those written for the general public are not regarded by most biologists as strictly representative. As a thinker he is more careless than Huxley, and as a result less critical and exact as a writer.

[Illustration: Fig. 122.--Ernst Haeckel, Born 1834.]

There can be no doubt that the germs of evolutionary thought existed in Greek philosophy, and that they were retained in a state of low vitality among the mediæval thinkers who reflected upon the problem of creation. It was not, however, until the beginning of the nineteenth century that, under the nurture of Lamarck, they grew into what we may speak of as the modern theory of evolution. After various vicissitudes this doctrine was made fertile by Darwin, who supplied it with a new principle, that of natural selection.

The fruits of this long growth are now being gathered. After Darwin the problem of biology became not merely to describe phenomena, but to explain them. This is the outcome of the rise and progress of biology: first, crude and uncritical observations of the forms of animated nature; then descriptive analysis of their structure and development; and, finally, experimental studies, the effort to explain vital phenomena, an effort in which biologists are at present engaged.

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