XVI THE HISTORY OF ZOOLOGY 675 



made during this period by Vicq d'Azyr, who enunciated the 

 principle of serial homology ; by Peter Camper, who investigated 

 the pneumaticity of the bones of Birds, and was the first to 

 apply exact methods of measurement to the human skull ; by 

 Alexander Monro, who greatly advanced our knowledge of the 

 anatomy of Fishes ; and by Poll, whose Testacea uhHusqioe Sicilice 

 is the most famous of the older works on Mollusca. And in the 

 domain of out-door zoology — the study of the actual life of animals 

 with but little regard to their structure or classification, or to the 

 broader scientific questions connected with them — special mention 

 must be made of Gilbert White, whose Natural History and 

 Antiquities of Selborne is a classic both in science and letters. 



The latter part of the eighteenth century is also specially re- 

 markable for the publication of the earliest scientific speculations 

 on the origin of species. The idea of evolution is to be found in 

 the works of more than one of the great Greek and Roman 

 philosophers, such as Empedocles (495 — 415 B.C.) and Lucretius 

 (99 — 55 B.C.); and the writings of some of the Fathers of the 

 Church, such as Augustine (353 — 430) and Thomas Aquinas 

 (1225 — 1274) seem to show that they had no objection to 

 " derivative creation," or evolution under direct Divine superin- 

 tendence. But by about the middle of the sixteenth century, the 

 idea of the immutability of specially created species had hardened 

 into a dogma which it was unsafe to question ; and, this state of 

 things continuing, the earliest of the great evolutionists, Buffon, 

 felt himself obliged to qualify all his speculations with a declara- 

 tion, sincere or ironical, of his belief that species were immutable. 

 Linnaeus, reckoning all higher groups as subjective, contended for 

 the real existence of species, saying " we recognise as many species 

 as were originally created," and this opinion was held by the vast 

 majority of naturalists, not only of his own time, but up to within 

 forty or fifty years of the present day. 



Buffon, bom in the same year (1707) as Linnaeus, was, in his 

 methods and ideas, the exact opposite of his great systematising 

 contemporary. He wrote charming accounts of the external 

 characters and habits of animals, but declined to classify them, 

 on the ground that all arrangements of the kind were arbitrary, 

 and that it was easier, more useful, and more agreeable to con- 

 sider the lower animals in relation to ourselves. On this prmciple, 

 he begins his Eistoire naturelle with Man, then takes up the 

 various domestic Mammals, and afterwards proceeds to consider 

 the less familiar forms. But he was essentially a philosophical 

 zoologist ; besides enunciating a theory of heredity, he grasped 

 the idea of homology, endeavoured to explain the facts of geo- 

 graphical distribution, and, in a tentative and guarded way, 

 admitted the mutability of species, and advanced a hypothesis 

 of their origin. His speculations refer mainly to the modification. 



