xvi THE HISTORY OF ZOOLOGY 683 



great interest, was too crude and speculative to make many 

 converts among men of science. But Darwin had the advantage 

 of being, not only a philosopher, but a naturalist in the broadest 

 sense a systematist with a sufficient knowledge of anatomy, 

 thoroughly conversant with the breeding of domestic animals and 

 cultivated plants, a keen observer of external nature, both organic 

 and inorganic, and with unrivalled experience as a traveller. 

 It is not surprising, therefore, that the wealth of illustration, 

 the close reasoning, and the philosophic spirit of the Origin, 

 converted the whole scientific world to the general doctrine of 

 transformism within twenty years. The theory of Natural 

 Selection, the Survival of the Fittest, or the Preservation of 

 Favoured Races in the Struggle for Life, was first grasped by Darwin 

 in 1838, but was not published until 1858, when it was announced 

 simultaneously by himself and by Alfred Russel Wallace. Both 

 these authors had, however, been anticipated by W. C. Wells 

 in 1813, and by Patrick Matthew in 1831. Darwin's other 

 works, especially The Variations of Animals and Plants under 

 Domestication and The Descent of Man, rank among the most 

 important contributions to philosophical Biology. With them 

 must be mentioned the luminous Principles of Biology of Herbert 

 Spencer, who consistently upheld the direct action of the en- 

 vironment as a factor in evolution. Wallace, on the other hand, 

 is a pure selectionist, while Darwin held "that natural selec- 

 tion has been the main but not the exclusive means of 

 modification." 



The additions to zoological knowledge made by the voyagers 

 of the eighteenth century have been referred to ; even more 

 important are the numerous great scientific expeditions of the 

 nineteenth and twentieth centuries. Among the most prominent 

 of these are the voyages of the French ships Astrolabe, Uranie, 

 Eonite and Geographe, in which researches were carried on by 

 Peron and La Sueur, Quoy and Gaimard, Eydoux and 

 Souleyet, and Hombron and Jacquinot, and given to the 

 world in splendidly illustrated folios. Still more famous is the 

 voyage of H.M.S. Beagle (1831-36), in which Darwin gained 

 his extraordinarily wide and accurate knowledge of natural 

 history, and the narration of which is published in his Naturalist's 

 Voyage. Other celebrated voyages are those of H.M.S. Rattle- 

 snake (1846-50), of which T. H. Huxley was assistant-surgeon ; 

 of H.M.SS. Erebus and Terror, accompanied by Sir J. D. Hooker ; 

 of the American " Wilkes " expedition, with J. D. Dana as 

 naturalist, and of the Austrian frigate Novara. But the most 

 famous and complete of all scientific voyages was that of 

 H.M.S. Challenger, in 1872-76, the five years' cruise of which 

 was marked by discoveries of great importance by the scientific 

 staff, Sir Wyville Thomson, John Murray, H. N. Moseley, 



