Part 15

Among primeval men, who obtained their food by hunting out such edible objects as were already in existence, war was universal. The supply of fruit, fish, and game being strictly limited, men were compelled to fight under penalty of starvation. As intelligence advanced and men learned to cultivate useful plants and to domesticate animals, and as they learned further to exchange by barter the products of their labor, a much greater population could live upon a given area. These tribes would be more powerful than their neighbors who still lived by hunting, fishing, and such like, and would flourish at their expense. Through agriculture and commerce men slowly learned that one man’s interest was not necessarily opposed to another’s; they also learned, though it may be ever so feebly, that fighting and plundering one another hindered rather than promoted their welfare. Thus man slowly evolved from a primitive, predatory civilization, in which war was universal and chronic, to the higher industrial civilization, in which war is much less frequent and less universal. Out of this primitive industrial civilization, which has grown more and more complex with the passing years, have come the arts and sciences, which give such added interest and value to modern life. This evolving industrial civilization, by furnishing a wider basis for political union through community of interest instead of mere blood-relationship, has greatly extended the field over which moral obligations are recognized as binding.[22] Social evolution is tending to eradicate more and more, through disuse, the brutish instincts of man; weakening his fighting propensities, his cruelty, his selfishness, his passions; and strengthening, by use, his sympathies, his kindness, his mercy, his sense of justice and honor, and his charity. The goal of social evolution seems to be _men of character_,—men with the widest possible knowledge of the laws of nature, physical, intellectual, and moral; and with the desire and will to rightly obey these laws. Such men will be both loving and lovable characters. In view of this may we not supplement Sir William Hamilton’s aphorism, and say that there is nothing great in mind but character? Since evolution is producing such characters, though it may be seemingly ever so slowly, is it again a shallow philosophy which teaches that there is a designer unfolding these characters? We do not think so. And if there is a designer who has been making towards this goal throughout the infinite sweep of bygone ages, do we not have at least some faint adumbration of knowledge as to the character of this designer? It seems to us that we do. Well may we say, with Matthew Arnold, that there is immanent in the cosmos an eternal soul, not ourselves, that makes for righteousness. This double assertion, that there is a soul in the universe outside of ourselves, and that this soul makes for right conduct, is the basis of fundamental importance in all religions. There are many religions in the world, and many creeds of the one great religion of christendom. They differ in many of the transcendental doctrines that they teach, and in many of the rules of conduct that they prescribe for their adherents; but they all contain as their most fundamental and vitally important basis the double assertion that there is a soul of the universe, and that this soul makes for right conduct. The assertion may be thickly overlaid with superstitions and petty rites by the untrained and dull intelligence of low races, as in the Eskimos; or it may attain a high degree of development and perfection, as among the Jews. The refinement and beauty of the double conception are more and more enhanced with social evolution. Just in proportion as civilization advances, and men come to reason more carefully and entertain wider views of life, just to that extent do they come to value more highly the essential truths of religion, while they attach less and less importance to many superficial details. It is of vastly greater moment to us that there is a cosmic soul in the universe that makes for righteousness than that this soul is threefold or onefold in its transcendental nature. Also of vastly more moment to us is a belief in this soul than any opinions we may entertain about eating meat on Friday or listening to attractive music on Sunday. A thoughtful mind, penetrated with the conviction of the truth of evolution, entertains views on all subjects pertaining to man, very different from those held by one not familiar with the great theory. His conceptions of the first Adam are profoundly modified by a flood of facts. If this flood sweep him on irresistibly, and equally profoundly modifies his conceptions of the second Adam, can it not be seen that even this is a fact of small significance compared with that other fact of overwhelming importance, viz.: the fact of the existence in the universe of a cosmic soul that makes for righteousness? Man is essentially a religious animal, and there is a very substantial philosophical basis for his religion.[23] His religion may be highly colored with emotion, or it may be coldly philosophical. When Herbert Spencer speaks of the eternal Power in the universe which makes for righteousness and is manifested in every event of the universe as the Unknowable, does he not do what Holy Writ has already done? “Canst thou find out the Almighty unto perfection?” When Carlyle speaks of the Universe as in very truth the star-domed city of God, and reminds us that through every crystal and through every grass blade, but most through every living soul, the glory of a present God still beams, he means much the same thing that Mr. Spencer does when he speaks of a Power that is inscrutable in itself, yet is revealed from moment to moment in every throb of the mighty rhythmic life of the universe. The only difference is that Mr. Spencer speaks in the colorless, precise, and formal language of science, while Carlyle’s language is colored by emotion; is, in fact, poetical.[24]

EVOLUTION AND SOCIAL PROBLEMS.

The relation of evolution to many social problems of vital importance is a fascinating as well as very extensive subject. We have only space to say that in order to understand the normal actions, as well as the abnormal ones, of the members of society, and in order, therefore, to understand and inaugurate rational methods of conducting education, minimizing pauperism, vice, disease, and crime, it must constantly be borne in mind that two great streams of tendencies have come down from the ages in the germ cells—what we may call the diseased and animal tendencies on the one hand, and the distinctively human and healthy tendencies on the other.

The most characteristic of the human tendencies are abstract thought and reflection, and therefore the power of choice or will, and altruism.

Also it must be borne in mind that environment is a force of commanding influence. This environment (which the individual may make for himself to a limited extent) may be propitious or adverse to the best human and normal tendencies. The relative preponderance of the animal or the human, the healthy, or the diseased tendencies, taken in conjunction with the character of the environment, stamp man’s actions as normal (and therefore right or wrong) or as abnormal, and therefore irresponsible. Not to discriminate between such normal and abnormal persons is not in accordance with either common morality or common sense. Neither is it in accord with common sense, or morality, or humanity, for society to deal with its habitual criminals and paupers, and subjects of hereditary disease, in the utterly irrational manner that it does. When society takes away from the criminal his personal liberty and places him in an environment that theoretically reforms him and protects itself, why does it not take cognizance of the fact that its theories are often woful failures in practice? The criminal is often not reformed and he gets into the category of habitual offenders; but society permits him, during his intervals of freedom, to procreate his kind and send his polluted cargoes of vicious heritages to helpless offspring. Is this humanity to these offspring? It is the grossest inhumanity! Does society protect itself by its intermittent detentions of habitual criminals? It probably breeds three habitual criminals while it is failing in its efforts to reform one. It is mostly by Nature’s prematurely killing off incorrigible criminals by their diseases and intemperance, that these social pests are kept within due bounds, and not through reformations accomplished in improperly conducted prisons. It seems to us that every consideration of justice and humanity cries aloud for the destruction of the procreating glands in _habitual criminals_.[25] Castration should go hand in hand with detention behind prison bars. Why should the habitual drunkard, for instance, be permitted to evolve his poisoned germ cells into helpless beings, giving them diseased bodies and vitiated moral characters, thus foredooming them to life-long physical ailments and moral turpitude? Removal of the procreating glands should be the penalty for chronic alcoholism. In objection to this suggestion, some may prate of personal liberty. What a multitude of outrages and brutalities the broad mantle of personal liberty is often made to cover! In allowing personal liberty to an undeserving individual, which more often means unbridled license to that individual, a whole generation of offspring are frequently enslaved by poverty, vice, crime, and disease in its manifold manifestations. During organic evolution Natural Selection has been incessantly on the watch for weaknesses of any kind, ruthlessly exterminating the helpless, the weak, the sick, and those that in any way are unfit. In social evolution Natural Selection has often been of necessity no less ruthless. But during social evolution characters that are unfolding more and more loving and lovable traits have so largely subordinated Natural Selection as to permit the helpless, the old, the sick, and the unfit, to live, thus strengthening those highest attributes of the greatest minds, viz.: intelligent sympathy, pity and love.

But it seems to us that the highest altruism, in dealing kindly with an abnormal, possible parent, will not continue long to stupidly overlook the weighty rights of unborn children. Human selection of the socially unfit will be dominated more and more, as social evolution unfolds its fruits, by those minds that are advancing to the highest goals of evolution, viz.: large minds of high character—widely informed minds, of strong will and broad sympathies. And under these circumstances we may hope that unborn generations will not be given over to total oblivion.

Well may we repeat, before concluding this little book, that man is not only a creature of the present, but profoundly a product of the abysmal ages of a bygone eternity. He is not only a composite chip of many old human blocks, but of innumerable geologic ancestral blocks. He has in his constitution simian, reptilian, piscine, and innumerable other chips, so to speak, and is indeed of the earth earthy; for studies in heredity not only illustrate the continuity of the human race, but also clearly indicate the continuity of this race with more lowly animals. Man has in his structure the indelible impress of the handiwork of these lowly relatives. Upon him, as upon them, and upon all living creatures, the forces of heredity and variation, of use and disuse, of environment and Natural Selection, have been and are perpetually playing, evolving him in one direction and innumerable creatures in other directions.

The goal of evolution seems to be men with Great Minds of High Character. _There is nothing great in the world but man, nothing great in man but mind, and nothing great in mind but character._

SECTION VII.

CLASSIFICATION OF ANIMALS AND PLANTS.

A SYNOPSIS OF THE ANIMAL KINGDOM.

In order that the reader may appreciate to some extent the relative positions of the different groups of animals, extinct and living, in the scale of life, the following brief classification may be useful. This synopsis is especially intended to help readers who are not familiar with elementary zoölogy to understand the significance of the different types of animals found in the strata of different geologic periods, and more particularly to grasp the meaning of the Diagram of Development. The animals are usually mentioned in the order of their position in the scale of life, commencing with the lowest and simplest.

SYNOPSIS OF GROUPS.

A. PROTOZOA. Unicellular animals, dissociated, or associated in simple, loose colonies of similar organisms. Many have an exoskeleton of lime, flint, or other material. Reproduction by fission and by temporary or permanent conjugation.

B. METAZOA. Multicellular animals, consisting of a large number of cells associated together to form single, complex individuals. The cells of an individual are usually differentiated into several kinds performing special functions. Reproduction in the higher forms is sexual; in the lower forms it is often by budding as well as sexual.

SYNOPSIS OF THE BRANCHES OF ANIMALS.

GROUP A. PROTOZOA.

Branch I.—=Protozoa.= Characteristics already defined.

Class 1.—_Monera._ Class 2.—_Rhizopoda_: Amœba, Arcella, Foraminifera, Difflugia, Quadrula. Class 3.—_Gregarinida_: Gregarina. Class 4.—_Infusoria_: Noctiluca, Paramecium, Stylonychia.

GROUP B. METAZOA.

Branch II.—=Porifera.= Sponges are animals with their cells arranged in two well-defined layers, one of which is internal (endoderm) and the other external (ectoderm). There is a middle stratum of cells (mesoglœa) which does not attain to the definiteness of a mesoderm. Sponges do not possess a body cavity (cœlome); they possess, essentially, a bilateral symmetry. The body varies greatly in shape, and is traversed by canals having large openings (oscula) and numerous small openings (pores) on the surface. The ectoderm is continued through the pores into afferent canals; the endoderm cells line most of the internal (efferent) cavities, and are mostly flagellate; the mesoglœa contains a skeleton of flint, lime, or spongin. Reproduction may be by budding or sexual (either hermaphroditic or unisexual).

Branch III.—=Cœlenterata.= Animals possessing radial symmetry. There is no body cavity (cœlome), but there is a primitive digestive cavity (enteron). The body consists of two layers, an ectoderm and endoderm; between these two layers there is a mesoglœa of jelly-like consistency; in the simplest cases there are no cells in the mesoglœa, but secondarily endodermal cells may migrate into it. Stinging cells are generally present.

There are two divergent types of structure. The more primitive one is the sessile tubular hydroid, which may be compared to a gastrula furnished at one end with a crown of tentacles surrounding the opening of the enteron, and fixed at the opposite end. The less primitive, derived form, is the active jellyfish (medusoid) type. The hydroid type often constructs a calcareous skeleton known as coral. One life history may present both types (alternation of generations). Reproduction is sexual or by budding, in the latter case often resulting in the formation of colonies.

Class 1.—_Hydrozoa_: Hydra, Jellyfish. Class 2.—_Actinozoa_: Sea-Anemones, Coral Polyps. Class 3.—_Ctenophora_: Comb-Bearers.

Branch IV.—=Echinodermata.= Animals, the larvæ of which possess bilateral symmetry, while the adults have radial symmetry. Even the adults exhibit to a varying extent a tendency to bilateral symmetry. Lime is always deposited in the mesodermic substance (mesenchyme). From the primitive digestive canals of the larvæ pouches grow out to form the usually spacious body cavity and the characteristic water vascular system. The latter and the nervous system exhibit generally a typical five-rayed arrangement. During development there is a distinction between mesoblast derived from gut pouches and mesenchyme produced from migrated amœboid cells. Complicated metamorphosis.

Class 1.—_Cystoidea._ Class 2.—_Blastoidea._ Class 3.—_Crinoidea_: Stone-lily. Class 4.—_Asteroidea_: Star-fishes. Class 5.—_Echinoidea_: Sea-urchins. Class 6.—_Holothuroidea_: Sea-cucumbers.

Branch V.—=Vermes.= The term “worms” includes a “heterogeneous mob,” a collection of classes whose relationships are poorly understood. But they are of great zoölogical interest, for, amid the diversity, there can be discerned affinities with Cœlenterata, Echinodermata, Arthropoda, Mollusca, and Vertebrata. They possess a well-defined mesoderm. They possess bilateral symmetry and have, as a rule, a head, tail, dorsal and ventral surfaces, and right and left sides. The lower worms are unsegmented. In the higher ones the digestive tract extends from the head to the end of the body; a dorsal vessel is usually present above the digestive tract; the nervous system consists of a supra-œsophageal ganglion (brain) and a simple or more commonly double, ventral, ganglionated cord; there is a body cavity (cœlome) lined with mesoderm; true jointed appendages are never present.

Class 1.—_Platyhelminthes_: Flat-worms. Class 2.—_Nemathelminthes_: Round-worms. Class 3.—_Rotatoria_: Rotifer. Class 4.—_Bryozoa._ Class 5.—_Brachiopoda_: Lampshells. Class 6.—_Nemertina._ Class 7.—_Enteropneusta_: Balanoglossus. Class 8.—_Gephyrea_: Star-worms. Class 9.—_Annulata_: Earth-worms, Leeches, Sea-worms.

Branch VI.—=Arthropoda.= Animals with bilateral symmetry. Bodies segmented, but not uniformly so. Several or all of the segments bear paired jointed appendages variously modified. Chitinous exoskeleton. Digestive canal beneath the heart. Supra-œsophagel ganglion (“brain”) connected by a nerve ring round the gullet with a double chain of ventral ganglia. Cœlome small in the adult. Sexes almost always separate. Often some metamorphosis.

Class 1.—_Crustacea_: Trilobites, Shrimps, Crabs. Class 2.—_Arachnida_: Spider, Scorpion. Class 3.—_Onychophora_: Peripatus. Class 4.—_Myriapoda_: Centipede. Class 5.—_Insecta_: Cockroach, Ants, Butterfly.

Branch VII.—=Mollusca.= Unsegmented animals, possessing, fundamentally, a bilateral symmetry. A very characteristic structure is the “foot”—a muscular protrusion of the ventral surface. Typically, a projecting fold from the dorsal surface of the body forms a mantle, or pallium; the mantle often secretes a single or double shell covering the viscera. The mantle and shell may both be absent. The central nervous system consists of paired ganglia with connecting commissures, viz.: cerebral, pleural, pedal, and visceral ganglia. Heart possesses two auricles and one ventricle. Respiration generally by gills. Frequently there are two larval stages. Development is often direct.

Class 1.—_Lamellibranchiata_: Clam, Oyster. Class 2.—_Scaphopoda._ Class 3.—_Gasteropoda_: Snail, Whelks, Slugs. Class 4.—_Amphineura_: Chitons. Class 5.—_Cephalopoda_: Squids and Cuttlefish.

Branch VIII.—=Vertebrata or Chordata.= Vertebrates are animals having a distinct body cavity (cœlome) and a segmental arrangement of parts. A hypoblastic skeletal notochord is always present in the embryo, but tends to be replaced by an axial skeleton of mesoblastic origin (backbone). Gill slits are always present in the embryo and may or may not persist in adult life. Gill-lamellæ do not occur above Amphibians. Heart is ventral. Central nervous system is dorsal. Eye begins to develop as an outgrowth from the brain.

Class 1.—_Tunicata._ Class 2.—_Leptocardii._ Class 3.—_Marsipobranchii._ Class 4.—_Pisces._ Class 5.—_Amphibia._ Class 6.—_Reptilia._ Class 7.—_Aves._ Class 8.—_Mammalia._

Class 1.—_Tunicata._ The tunicates are remarkable animals, and seem to stumble on the border line between Invertebrates and Vertebrates. Their vertebrate characteristics—gill slits, notochord, dorsal nervous system, and brain eye—are generally discernible only in the free-swimming larval state. They generally degenerate as they progress towards the adult condition, and diverge greatly from the vertebrate type. They are mostly stationary. They are multicellular animals possessing bilateral symmetry. The body is enveloped by a thickened cuticle containing cellulose. The pharynx, perforated with the gill slits, is surrounded by a peribranchial chamber (atrium) which communicates with the exterior by an atrial opening. Heart is simple and tubular. The nervous system is generally reduced to a single ganglion. Nephridia are absent. Hermaphrodites. Usually a metamorphosis.

Class 2.—_Leptocardii._ Simple, worm-like vertebrate animals represented by a single distinct type—amphioxus or lancelet. The central nervous system consists of a spinal cord, and a very ill-defined, rudimentary brain. No skeleton other than an unsegmented and persistent notochord which projects beyond the anterior end of the nerve cord. No scales. Gill slits are very numerous in the adult. Amphioxus is widely removed from the fishes by the absence of skull, jaws, definite brain, sympathetic nervous system, ear, eye, genital ducts, spleen, and definite heart, the latter being simple and tubular. No pectoral or pelvic limbs (fins). Blood colorless; gastrula ciliated and free-swimming. Metamorphosis.

Class 3.—_Marsipobranchii._ Worm-like vertebrates having round mouths without distinctly developed jaws; no jaw-bones. Without scales and without paired limbs (fins). Six or seven gill pouches. Skeleton consists of persistent, unconstricted, cartilaginous notochord. No sympathetic nervous system. Single nasal sac. No conus arteriosus, no spleen or pancreas. Undivided segmental duct.

Class 4.—_Pisces._[26] Aquatic, cold-blooded vertebrates, with a movable lower jaw. Cartilaginous or osseous skeleton, with paired pectoral and pelvic fins, supported by fin rays (_radials_ diverging from several _basal_ pieces); also unpaired fins. No sternum. Exoskeleton of bony plates or scales. Skull has usually one occipital condyle. Breathing by permanent gills attached to gristly or bony arches on the sides of the gill clefts. In most fishes the digestive cavity gives origin to an air bladder which may or may not remain permanently connected with the digestive cavity. It mostly serves a hydrostatic purpose, but in some of the more primitive fishes (Amia, Lepidosteus) it is occasionally of some slight use in respiration. Heart consists of single auricle and single ventricle, and contains only venous blood; there is a sinus venosus and often a conus arteriosus. No inferior vena cava. No allantois. Most fishes lay eggs which are fertilized in the water.

Sub-class 1.—_Elasmobranchii._ Order 1.—_Plagiostomi_: Sharks, Rays. Order 2.—_Holocephali_: Chimæroids. Sub-class 2.—_Teleostomi._ Order 1.—_Crossopterygii_: Polypterus, Calamoichthys. Order 2.—_Ganoidei_: Sturgeon, Garpike, Amia, Polyodon. Order 3.—_Dipnoi_: Lung-fishes, e. g., Ceratodus, Protopterus, and Lepidosiren. Order 4.—_Teleostei_: Perch, Cod, Salmon, Eel.

Class 5.—_Amphibia._ In the evolution of vertebrates the Amphibians represent those forms which made the transition from aquatic to terrestrial life, but have lingered near the water. Certain acquisitions gained by the Dipnoi, such as a three-chambered heart and lungs, have been accentuated and firmly established by the Amphibians.

Amphibia are cold-blooded vertebrates whose larval forms always have gill arches bearing gills. In some forms the gills are retained throughout life, though the adults always possess functional lungs. Nasal sacs open posteriorly into the mouth. In existing forms there is rarely any exoskeleton. There are two occipital condyles. Unpaired fins are frequently present, though they possess no fin rays. When limbs are present they possess distinct digits and conform to the same type as those of the higher vertebrates. Heart has two auricles and one ventricle. There is an inferior vena cava. The intestine ends in a cloacal chamber, as do also the urinogenital ducts. Eggs almost always laid in the water. Often a marked metamorphosis.

Order 1.—_Urodela._ Amphibia which retain the tail throughout life. The order is subdivided into: a. _Perennibranchiata_, which retain the gills throughout life: _Siren_, _Proteus_. b. _Caducibranchiata_; no persistent gills: _Triton_, _Salamandra_. Order 2.—_Gymnophiona._ Body snake-like; no feet; young with gills: _Cœcilia_. Order 3.—_Stegocephala._ Extinct forms: _Archegosaurus_. Order 4.—_Anura._ Tailless amphibia; body short, with four limbs; larvæ tailed: _Frog_, _Toad_.

Class 6.—_Reptilia._ Cold-blooded, air-breathing vertebrates. Limbs usually ending in claws; limbs sometimes absent; exoskeleton of scales; ribs well developed; incomplete double circulation; heart is four-chambered in the highest forms; oviparous; no metamorphosis; embryo with an amnion and allantois.

The following are some of the orders that have become extinct, viz.:

a. _Theromorpha_: Mammal-like saurians. b. _Ichthyosauria_: Swimming saurians. c. _Pterosauria_: Flying saurians. d. _Dinosauria_: Colossal land saurians capable of rising and resting on the hind legs.

The following are the living orders, viz.: a, _Ophidia_; b, _Lacertilia_; c, _Chelonia_; d, _Crocodilia_.

Class 7.—_Aves._ Feathered vertebrata; heart four-chambered; warm-blooded; lungs with accessory air-sacs; bones dense and hollow; jaws encased in horny beaks in modern forms; the fore-limbs form wings; oviparous; eggs are very large and covered by calcareous shell.

Sub-class 1.—_Saururæ_: Archæopteryx. Sub-class 2.—_Odontornithes_: Ichthyornis, Hesperornis. Sub-class 3.—_Ratitæ_: Smooth sternum. Sub-class 4.—_Carinatæ_: Keeled sternum.

Class 8.—_Mammalia._ Animals having the body covered with hair; warm-blooded; young nourished with milk secreted from mammary glands; lower jaw articulating directly with the skull, the quadrate becoming the malleus (ear-bone); heart four-chambered and with the aorta reflected over the left bronchus; red blood-corpuscles non-nucleated; complete diaphragm; brain large, especially the cerebrum and cerebellum; uterine gestation; viviparous.

Sub-class 1.—_Ornithodelphia_: Order Monotremes. Urinary and genital canals opening into cloaca. Laying large eggs. Sub-class 2.—_Didelphia_: Order Marsupials. Animals having pouch for protection and growth of prematurely born embryos. Sub-class 3.—_Monodelphia_: Placental Mammals. Order 1.—_Edentata._ Order 2.—_Rodentia._ Order 3.—_Insectivora._ Order 4.—_Cheiroptera._ Order 5.—_Cetacea._ Order 6.—_Sirenia._ Order 7.—_Proboscidea._ Order 8.—_Hyracoidea._ Order 9.—_Ungulata._ Order 10.—_Carnivora._ Order 11.—_Primates._