INTRODUCTION. \{ 



c'est pour elle un moyen sans homes avec lequel ellefait les plus grandes choses comme 

 les moindres." 



In 1809 Lamarck published his Philosophies Zoologique. This wofk comprised 

 the results of his speculations as well as of his special work of concise description, 

 determination, and classification of vegetable and animal species. He was struck with 

 the differences, but still more with the resemblances in animals; he noticed their 

 variations, and, as Martins has said, a triple impression was made on his mind : the 

 certainty of the variability of species under the influence of external agencies; 

 that of the fundamental unity of the animal kingdom ; finally, the probability of the 

 successive generation of different classes of animals, arising, so to speak, one from 

 another, like a tree whose branches, leaves, flowers, and fruits are the results of 

 successive evolutions of a single organ, — the seed or bud. 



All this was however speculation, a priori, premature guesses without a broad basis 

 of facts. The fulness of time had not yet come. The year 1809 was long ante- 

 rior to the general use of the microscope, before the sciences of embryology, of his- 

 tology, the doctrine of the cell, and before the principles of palaeontology and zoo- 

 geography had been founded. Lamarck was almost forgotten, his speculations had 

 been treated with silent contempt or indifference. A period of over half a century 

 succeeded, an age of busy search for facts, a period prolific in inductive sciences, — a 

 sisterhood of knowledge as numerous as the family of Niobe. In the year 1859, 

 Darwin, Wallace, Bates, and among botanists, Hooker, unanimously insisted on the 

 fact of the variation of species and their origin by natural causes ; and they supported 

 their views by special more or less limited theories. Darwin's theory of natural selec- 

 tion was adopted with a rapidity and unanimity unparalleled in the history of science. 

 We will now examine the general alignment, and state some of the general principles 

 upon which the modern scientific theory of descent is based. 



There are three laws or inductions supporting the theory : 1. Change in the envi- 

 ronment of the organism, involving adaptation to such change. 2. Transmission by 

 heredity of ancestral together with acquired traits. 3. The selection of useful traits 

 and their preservation and fixity. Around each of these leading principles cluster 

 others accessory and indispensable, and doubtless still others may yet be discovered. 



The recognition of two factors have attracted fresh attention to the theory of 

 descent, and caused it to be generally accepted as a working theory indispensable to 

 biological science ; these are (1) the facts of variation with the difiiculty of limiting 

 species and genera, and the discovery of connecting links between the higher groups 

 of animals, including orders, classes, and sub-kingdoms ; and (2) the influence on the 

 plant or animal of a change in the environment. The second of these factors was 

 advocated by Lamarck and St. Hilaire. Since the publication of Darwin's special 

 theory of natural selection, which was accepted as a vera causa by the large propor- 

 tion of naturalists, a few have not been satisfied with this theory alone, but have in 

 various directions gone back of Darwin and natural selection to views like those of 

 Lamarck, whether they were acquainted with his theory and works or not. Darwhi 

 took the tendency to variation as the foundation upon which to erect the superstruc- 

 ture of natural selection ; others have sought to account first for the tendency to varia- 

 tion, and then given natural selection its due place as a secondary, though important, 

 phase. Had Lamarck, with his unquestioned ability as a thinker and observer, lived at 

 the present time, when so many new sciences have arisen, and the older ones of chem- 

 istry and physics have been revolutionized, he would have checked his imagination 



