EXPLANATION OF RUDIMENTS.

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rudimentary organs found in so many animals, of pointing out their bearing on the theory of transmutation. According to him, they were clearly the relics of parts which had been serviceable in some remote ancestor and had been reduced in size by disuse, and he rejected the idea as puerile that useless organs had been created for the sake of uniformity of plan." In truth, there is absolutely no scientific explanation for these rudimentary structures other than that of inheritance from a common ancestral form and gradual suppression by disuse, because of subjection to conditions, in which they are no longer of avail.

We have dwelt at length upon the most marked examples of these strange traces, without having by any means exhausted the list, because of their peculiar significance in the interpretation of the development of life. What the germ is to the future, is the relic to the past. Rudiments are like the blocks of ancient temples incorporated into the modern edifices which have taken their place. But they differ from them in being of no use. They are fragments of the crumbling columns of antiquity.

No testimony is more convincing of man s place in nature than that so speakingly furnished by these rudimentary structures. For, as Mr. Darwin has eloquently expressed it, (I take the liberty to interpolate a single line), by them we see that man with all his noble qualities, with sympathy that feels for the most abject, with benevolence which extends not only to his fellow-man, but to the humblest living thing on earth, with an imagination that outrivals and mocks for expression his marvelous gift of speech, with a God-like intellect which has penetrated to the structure and movements of the heavenly bodies-man, with all these exalted powers-still bears indelible, in every organ of his frame, the stamp of his lowly birth.

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THE EVOLUTION OF FORMS OF LIFE.

LECTURE V.

THE EVOLUTION OF FORMS OF LIFE.

CONTENTS.

The Law of Inheritability-Transmission of Acquired Defects-Homochronous Transmission-Atavism-The Physics of ReproductionAdaptation to External Conditions-Difficulty of Classification-Artificial Selection-The Struggle for Existence-Natural SelectionProtective Colors-Warning Colors-Sexual Selection-Complications in Natural Selection-Preservation of the Individual and of the Race -General Summary.

In concluding our consideration of the evolution of life we have to-day to study the forces or laws which preserve, perfect and diversify its forms. I desire to state, at the start, that though I shall quote from very many authorities, I am indebted for many of the facts which I shall present you to-day, to the publications of Darwin, and for most of them to the Natürliche Schöpfung's-geschichte (History of Creation) of Haeckel, a work so complete and comprehensive, as to have elicited from Mr. Darwin the statement, in the preface to his Descent of Man, "If this work had appeared before my essay had been written, I should probably never have completed it." I am led to present you this aspect of the subject simply to complete the evidence for evolution with its most important proof.

The overshadowing law which insures the perpetuity of form is that of

Inheritability.

That "like begets like" is a proverb in every language. The law of inheritance is so universally recognized and acknowledged as to be accepted as a matter of course. It is

THE PERPETUATION OF FORM.

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the breach and not the observance of the law which makes it the subject of comment. The birth of a child with webbed or supernumerary fingers or toes calls up the history of the remote ancestry in its explanation. The cohesion of the family, which is the safeguard of the state and nation, rests upon the acceptance of the principle of heredity. The law of heredity, if we may be allowed to coin the word, secures to the offspring not only the reproduction of the general form of the parent, but also the exact repetition of every physical and mental feature, characteristic of the parent. There were families in Rome which received from the shape of the nose or lips the titles of the nasones, labeones, buccones, etc. Aquiline noses are still transmitted among the posterity of the Bourbons. The Hapsburg (Austria) lip is a peculiarity worthy of mention in this connection. The Prussian kings are noted for their stature. Obesity, color, temperament, longevity, are all strictly transmitted by heredity. Vices of conformation, deformities, diseases, are alike reproduced in the offspring; moles, freckles, tumors, appear in the offspring in exactly the same spots as in the parents. The ancestral history is carefully examined by the physician in establishing his diagnosis of disease. Affections of the respiratory organs, e. g., tuberculosis; of the glands, scrofula; of the nervous system, epilepsy, are especially liable to be propagated in the offspring. Traits of mind are transmitted with equal fidelity. The family of Miltiades furnished heroes, of Pericles politicians. In the family of Bach there were no less than twenty-two musicians. For a generation the name of Graefe was venerated in medicine in Berlin, and in Boston generations of Warrens have been distinguished physicians. So for generations the Rothschilds have been renowned for a special talent in the acquisition of wealth. The horrible cruelties of the Borgias are counterbalanced in some degree, to the credit of Italy,

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TRANSMISSION OF ACQUIRED DEFECTS.

by the refinement and culture of the Florentine Medici. It is hardly necessary to state that the law of transmission holds with equal force throughout the animal and vegetable kingdoms. Albinoes, i. e., animals devoid of color, have been propagated as a separate species among rabbits and mice, as well as among men. Paraguay is noted for a special race of hornless oxen, bred from a bull born in 1770 without horns. The harmless character of the animal made it the subject of special selection in breeding, until a whole race was thus obtained. The well-known case of the otter sheep in our own country is a good illustration of the force of heredity. A Massachusetts farmer discovered one day among his flock an individual sheep "with a surprisingly long body and short and crooked legs." It occurred to the farmer that this development would be advantageous in rendering leaping impossible and thus checking depredations upon a neighbor's property. He forthwith bred from this individual with the desired result, and his neighbors following his example, the sheep of Massachusetts soon became noted for their staid decorum and profound respect for others' lands.

Transmission of Acquired Defects.

Even acquired defects are sometimes transmitted. Thus Brown-Séquard produced epilepsy in some guinea-pigs by injuring certain parts of their brains, and this artificallyinduced epilepsy appeared spontaneously in all the offspring of the diseased animals. Haeckel states that a race of tailless dogs was once propagated by persistently cutting off the tails of both sexes of the dog for several generations. The same author narrates that a few years ago, on an estate near Jena, a bull had his tail wrenched off by the careless slamming of a stable door, and "all the calves begotten of this bull were born without a tail."

ATAVISM.

Homochronous Transmission.

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So strong is the force of heredity, that diseases and defects are not only transmitted, but they are transmitted homochronously, that is, to appear in the offspring at the same age in which they were manifested in the parents. Diseases of the lungs, liver and brain occur in the child at the same period of life as in the parent before it.

Atavism.

But under the laws of heredity the offspring may resemble not so much its parents as its grandparents, or ancestry even more reniote. This is the phenomenon of atavism, as it is called. How many peculiarities or eccentricities might we not be able to explain, if we could only sum up all the atoms of being that have come down to us from the bodies of our ancestors in regular line. Oliver Wendell Holmes bases several of the best characters in his novels upon the influence of heredity as far back as can be traced. We observe this phenomenon of atavism in the everyday history of some of the lower animals and plants. The planarian worms, for instance, as well as the ferns and mosses, beget forms entirely different from themselves, and it is only in the offspring of these different forms that the image of the first parents is reproduced. This alternation of generation was first remarked by the poet Chamisso, during his voyage around the world in 1819, in the case of the salpæ, small transparent structures, which float like particles of glass on the surface of the sea. In studying the habits and life history of these animals, Chamisso observed that the parent form, which has an eye of crescent or horseshoe-shape, produces offspring with cone-shaped eyes, but in the offspring of the offspring, the grand-children, so to speak, the original eye of horseshoe-shape reappears. Among other animals a