24 GENERAL riilNOIPLES OF ZOOLOGY. 



to the time of his death in 1882. He was incessantly busy in 

 developing his conception of the origin of species, and in collect- 

 ing for this a constantly increasing array of facts. The first 

 written notes, the fundamental ideas of which he communicated 

 to friends, particularly the geologist Lyell and the botanist 

 Hooker, were made in 1844, but the author was not persuaded to 

 give them publicity. Not until 1858 did Darwin decide to make 

 his first contribution to science. In this year he received an essay 

 sent by the traveller Wallace, which in its most important points 

 coincided with his own views. At the same time with Wallace's 

 manuscript an abstract of Darwin's theory was published. In the 

 next year (1859) appeared the most important of his writings, 

 "On the Origin of Species by means of Natural Selection," and 

 in rapid succession a splendid series of works, the fruit of many 

 years of preparatory labors. For the history of the theory the 

 most imjjortant of these are: (1) "Upon the Variation of Plants 

 and Animals under Domestication," two volumes, which chiefly 

 contain a collection of material for proofs; (2) on "The Descent 

 of Man," a work which gives the application of the theory to man. 



No scientific work of this century has attracted so much atten- 

 tion in the zoological, we may even say in the whole educated 

 world, as "The Origin of Species." It was generally received as 

 something entirely new, so completely had the scientific tradition 

 been lost. In professional circles it was stoutly combated by one 

 faction, with another it found well-wishing but hesitating accept- 

 ance. Only a few men placed themselves from the beginning in 

 a decided manner on the side of the great British investicjator. 

 There was a lively scientific battle, which ended in a brilliant vic- 

 tory for the theory of evolution. At the present time all our 

 scientific thoughts are so permeated with the idea of evolution that 

 we can scarcely speak of any considerable opposition to it. 



Post-Darwinian Writers. — Among the men who have most 

 influenced this rapid advance is to be mentioned, besides A. E. 

 Wallace, the co-founder of Darwinism, above all Ernst Haeckel, 

 who in his "General Morphology " and his "Natural History of 

 Cireation " has done much towards the extension of the theorv. 

 Among other energetic defenders of the theory in Germany should 

 be mentioned Fritz Muller, Carl Vogt, AVeismann, IMoritz Wao-uer, 

 and Nageli, even if they have taken special standpoints in refer- 

 ence to the causes conditioning the changes of form. Anion"- the 

 English naturalists are to be named particularly Huxlev, Hooker, 

 and Lyell. In America Gray, Gojie, and Hyatt were early sup- 



