X 



THE INFLUENCE OF DARWIN ON THE 

 STUDY OF ANIMAL EMBRYOLOGY 



By a. Sedgwick, M.A., F.R.S. 



Professor of Zoology and Comparative Anatomy in the 

 University of Cambridge. 



The publication of The Origin of Species ushered in a new era in i 

 the study of Embryology. Whereas, before the year 1859 the facts of i 

 anatomy and development were loosely held together by the theory 

 of types, which owed its origin to the great anatomists of the pre- 

 ceding generation, to Cuvier, L. Agassiz, J. Miiller, and R. Owen, 

 they were now combined together into one organic whole by the 

 theory of descent and by the hypothesis of recapitulation which was 

 deduced from that theory. The view^ that a knowledge of embryonic 

 and larval histories would lay bare the secrets of race-history and 

 .enable the course of evolution to be traced, and so lead to the 

 discovery of the natural system of classification, gave a powerful 

 stimulus to morphological study in general and to embryological 

 investigation in particular. In Darwin's M'ords: "Embryology rises 

 "greatly in interest, when we look at the embryo as a picture, 

 more or less obscured, of the progenitor, either in its adult or larval 

 state, of all the members of the same great classl" In the period 

 under consideration the output of embryological work has been 

 enormous. No group of the animal kingdom has escaped exhaustive 

 examination and no effort has been spared to obtain the embryos of 

 isolated and out of the way forms, the development of which might 

 have an important bearing upon questions of phylogeny and classifi- 

 cation. Marine zoological stations have been established, expeditions 

 have been sent to distant countries, and the methods of investigation 

 have been greatly improved. The result of this activity has been 

 that the main features of the developmental history of all the most 

 important animals are now known and the curiosity as to develop- \ 

 mental y)rocesses, so greatly excited by the j)rumulgati<)n of the \ 

 Darwinian theory, has to a considerable extent been satisfied. 



' First clearly enunciattd liy Fritz Miiller in Lis well-known work, Fur Darwin, 

 Leipzig, 18C4 ; (EdkIIsIi Edition, Pact* for Darwin, 186'J). 

 « Origin (6th edit.), p. 396. 



