William A. Locy

“ Species.—Since the question of the fixity of species is the central one in theories of evolution, it will be worth while to quote Lamarck's definition of species: "All those who have had much to do with the study of natural history know that naturalists at the present day are extremely embarrassed in defining what they mean by the word species.... We call species every collection of individuals which are alike or almost so, and we remark that the regeneration of these individuals conserves the species and propagates it in continuing successively to reproduce similar individuals." ”

“ The doctrine that all tissues of animals and plants are composed of aggregations of these units, and the derivatives from the same, is known as the cell-theory. It is a generalization which unites all animals and plants on the broad plane of similitude of structure, and, when we consider it in the light of its consequences, it stands out as one of the great scientific achievements of the nineteenth century. There is little danger of overestimating the importance of this doctrine as tending to unify the knowledge of living organisms. ”

“ Sweep of the Doctrine of Evolution.—The great sweep of the doctrine of evolution makes it "one of the greatest acquisitions of human knowledge." There has been no point of intellectual vantage reached which is more inspiring. ”

“ Embryology is one of the most important biological sciences in furnishing clues to the past history of animals. Every organism above the very lowest, no matter how complex, begins its existence as a single microscopic cell, and between that simple state and the fully formed condition every gradation of structure is exhibited. Every time an animal is developed these constructive changes are repeated in orderly sequence, and one who studies the series of steps in development is led to recognize that the process of building an animal's body is one of the most wonderful in all nature. ”

“ That the solution of the underlying question in evolution will still require a long time is evident; as Whitman said in his address before the Congress of Arts and Science in St. Louis in 1904: "The problem of problems in biology to-day, the problem which promises to sweep through the present century as it has the past one, with cumulative interest and correspondingly important results, is the one which became the life-work of Charles Darwin, and which can not be better or more simply expressed than in the title of his epoch-making book, The Origin of Species." ”

“ The observers were not long in recognizing that some of the greatest beauties of organic architecture are displayed in the internal structure of insects. The delicate tracery of the organs, their minuteness and perfection are well calculated to awaken surprise. Well might those early anatomists be moved to enthusiasm over their researches. Every excursion into this domain gave only beautiful pictures of a mechanism of exquisite delicacy, and their wonder grew into amazement. ”

“ The theory of organic evolution relates to the history of animal and plant life, while Darwin's theory of natural selection is only one of the various attempts to point out the causes for that history's being what it is. An attack upon Darwinism is not, in itself, an attack upon the general theory, but upon the adequacy of his explanation of the way in which nature has brought about the diversity of animal and plant life. ”

“ Huxley, when he felt the call, at a great personal sacrifice, to lay aside the more rigorous pursuits of scientific research, and to devote himself to molding science into the lives of the people, said of Balfour: "He is the only man who can carry out my work." ”

“ When we reflect on the part played in the body by the blood, we readily see that a correct idea of how it carries nourishment to the tissues, and how it brings away from them the products of disintegrated protoplasm is of prime importance in physiology. It is the point from which spring all other ideas of the action of tissues, and until this was known the fine analysis of vital processes could not be made. The true idea of respiration, of the secretion by glands, the chemical changes in the tissues, in fact, of all the general activities of the body, hinge upon this conception. ”

“ He insisted upon observation and experiment, and upon the necessity of studying the development of plants in order to understand their anatomy and physiology. He speaks scornfully of the botany of mere species-making as follows:
"Most people of the world, even the most enlightened, are still in the habit of regarding the botanist as a dealer in barbarous Latin names, as a man who gathers flowers, names them, dries them, and wraps them in paper, and all of whose wisdom consists in determining and classifying this hay which he has collected with such great pains." ”

“ The evidence is clear that untold generations of living forms, now preserved as fossils, inhabited the earth, disported themselves, and passed away long before the advent of man. The knowledge of this fossil life, on account of its great diversity, is an essential part of biology, and all the more so from the circumstance that many forms of life, remains of which are exhibited in the rocks, have long since become extinct. No history of biology would be complete without an account of the rise and progress of that department of biology which deals with fossil life. ”

“ Just as a knowledge of the construction of a machine is necessary to understand its action, so the anatomical analysis of an organ must precede a knowledge of its office. The term "physiological anatomy of an organ," so commonly used in text-books on physiology, illustrates the point. We can not appreciate the work of such an organ as the liver without a knowledge of the arrangement of its working units. The work of the anatomist concerns the statics of the body, that of the physiologist the dynamics; properly combined, they give a complete picture of the living organism. ”

“ It was in that century that the use of the microscope made known the similarity in cellular construction of all organized beings; that the substance, protoplasm, began to be recognized as the physical basis of life and the seat of all vital activities; then, most contagious diseases were traced to microscopic organisms, and as a consequence, medicine and surgery were reformed; then the belief in the spontaneous origin of life under present conditions was given up; and it was in that century that the doctrine of organic evolution gained general acceptance. ”

“ Owen's distinction between germ-cells and body-cells, made in 1849, was not of much importance, but in the theory of Weismann it is of vital significance. The germ-cells are the particular ones which carry forward from generation to generation the life of the individual. The body-cells are not inherited directly, but in the transmission of life the germ-cells pass to the succeeding generation, and they in turn have been inherited from the previous generation, and, therefore, we have the phenomenon of an unbroken connection with all previous generations. ”

“ There is no reason to think that the continuity is broken in the case of man's development. Naturalists have now come to accept as a mere statement of a fact of nature that the vast variety of forms of life upon our globe has been produced by a process of evolution. If this position be admitted, the next question would be, What are the factors which have been operative to bring this about? This brings us naturally to discuss the theories of evolution. ”

“ If, therefore, we wish to understand an organ or an animal, we must follow its development, and see it in simpler conditions, before the great modifications have been added.
The tracing of the stages whereby cells merge into tissues, tissues into organs, and determining how the organs by combinations build up the body, is embryology. On account of the extended applications of this subject in biology, and the light which it throws on all structural studies, we shall be justified in giving its history at somewhat greater length than that adopted in treating of other topics. ”

“ He supposed that these cataclysms of nature resulted in the extinction of all life, and that after each catastrophe the salubrious condition of the earth was restored, and that it was re-peopled by a new creation of living beings. This conception, known as the theory of catastrophism, was an obstacle to the progress of science. It is to be regretted that Cuvier was not able to accept the views of his illustrious contemporary Lamarck, who believed that the variations in fossil life, as well as those of living forms, were owing to gradual transformations. ”

“ Between Harvey and Wolff, embryology had become dominated by the theory that the embryo exists already pre-formed within the egg, and, as a result of the rise of this new doctrine, the publications of Wolff had a different setting from that of any of his predecessors. It is only fair to say that to this circumstance is owing, in large part, the prominence of his name in connection with the theory of epigenesis. [Pg 206] As we have already seen, Harvey, more than a century before the publications of Wolff, had clearly taught that development is a process of gradual becoming. ”

“ The Fabrica of Vesalius was a piece of careful, honest work, the moral influence of which must not be overlooked. At any moment in the world's history, work marked by sincerity exercises a wholesome influence, but at this particular stage of intellectual development such work was an innovation, and its significance for progress was wider and deeper than it might have been under different circumstances. ”

“ The work founded on selfish motives and vanity has sooner or later fallen by the wayside. We can recognize now that the work of scientific investigation, subjected to so much hostile criticism as it appeared from time to time, was undertaken in a reverent spirit, and was not iconoclastic, but remodelling in its influence. Some of the glories of our race are exhibited in the lives of the pioneers in scientific progress, in their struggles to establish some great truth and to maintain intellectual integrity. ”

“ If we now turn to comparative anatomy, to classification, and to the geographical distribution of animals, we find that it is necessary to assume the doctrine of descent in order to explain the observed facts; the evidence for evolution, indeed, becomes cumulative. But it is not necessary, nor will space permit, to give extended illustrations from these various departments of biological researches. ”

“ Working biologists will be the first to admit that it is not demonstrated by indubitable evidence, but the weight of evidence is so compelling that scientific men as a body regard the doctrine of organic evolution as merely expressing a fact of nature, and we can not in truth speak of any considerable opposition to it. ”

“ The recognition that both heredity and the process of evolution can be subjected to experimental tests was a revelation. Darwin and the early evolutionists thought the evolutionary changes too slow to be appreciated, but now we know that many of the changes can be investigated by experiment. Numerous experiments on heredity in poultry (Davenport) , in rats, in rabbits, and in guinea-pigs (Castle) have been carried out—experiments that test the laws of ancestral inheritance and throw great light upon the questions introduced by the investigations of Mendel and De Vries. ”

“ Weismann expresses the opinion that "the theory of descent is the most progressive step that has been taken in the development of human knowledge," and says that this position "is justified, it seems to me, even by this fact alone: that the [Pg 367] evolution idea is not merely a new light on the special region of biological sciences, zoölogy and botany, but is of quite general importance. The conception of an evolution of life upon the earth reaches far beyond the bounds of any single science, and influences our whole realm of thought. ”

“ Inheritance.—Lamarck's view of heredity was uncritical; according to his conception, inheritance was a simple, direct transmission of those superficial changes that arise in organs within the lifetime of an individual owing to use and disuse. It is on this question of the direct inheritance of variations acquired in the lifetime of an individual that his theory has been the most assailed. The belief in the inheritance of acquired characteristics has been so undermined by experimental evidence that at the present time we can not point to a single unchallenged instance of such inheritance. ”

“ Everything which has come to pass is on that part so far exposed, and everything in the future is still covered, but will appear in due course of time; thus the designation of evolution as "the unrolling of the scroll of the universe" becomes picturesquely suggestive. In its wide meaning, it includes the formation of the stars, solar systems, the elements of the inorganic world, as well as all living nature—this is general evolution; but the word as commonly employed is limited to organic evolution, or the formation of life upon our planet. ”

“ Now, egg and sperm are the two germinal elements which unite in development. Fertilization takes place by the union of sperm and egg, and inasmuch as the nuclei of each of these structures contain one-half of the number of chromosomes characteristic of the species, [Pg 313] their union in fertilization results in the restoration of the original number of chromosomes. The fertilized ovum is the starting-point of a new organism, and from the method of its fertilization it appears that the parental qualities are passed along to the cells of every tissue. ”

“ The spectacle afforded by the wonderful energies imprisoned within the compass of the microscopic cell of a plant, which we commonly regard as a merely passive organism, is not easily forgotten by one who has watched its movement hour by hour without pause or sign of weakening. The possible complexity of many other organisms seemingly as simple as the protoplasm of the plant just mentioned dawns upon one, and the comparison of such activity to that of higher animals loses much of its startling character. ”

“ The growth of the knowledge of organic nature is a long story, full of human interest. Nature has been always the same, but the capacity of man as its interpreter has varied. He has had to pass through other forms of intellectual activity, and gradually to conquer other phases of natural phenomena, before entering upon that most difficult task of investigating the manifestations of life. It will be readily understood, therefore, that biology was delayed in its development until after considerable progress had been made in other sciences. ”

“ Selection by nature does not mean the formation and preservation of the ideally perfect, but merely the survival of those best fitted to their environment.
Color.—The various ways in which natural selection acts are exceedingly diversified. The colors of animals may be a factor in their preservation, as the stripes on the zebra tending to make it inconspicuous in its surroundings. The stripes upon the sides of tigers simulate the shadows cast by the jungle grass in which the animals live, and serves to conceal them from their prey as well as from enemies. ”