406 A CENTURY OF SCIENCE 



organism meant a living witness of some great natural 

 law, in the interpretation of which zoology was engaged. 

 The organism in its structure, in its development, in its 

 habits furnished links in the chain of evidence which, 

 when completed, would reveal the meaning of nature. Of 

 all Agassiz 's pupils, probably William K. Brooks most 

 fittingly perpetuated his master's ideals. 



Period of Morphology and Embryology, 2847-1870. 



The new aspect of zoology which came as a result of 

 the influence of Agassiz characterized the zoological work 

 of the fifties and sixties, that is, until the significance 

 of the natural selection theory of Darwin and Wallace 

 became generally appreciated. 



The work in these years and well into the seventies was 

 largely influenced by the morphological, embryological 

 and systematic studies of Louis Agassiz and his school. 

 The structure, development, and homologies of animals 

 as indicating their relationship and position in the 

 scheme of classification was prominent in the work of 

 this period. The adaptations of animals to their envi- 

 ronment and the application of the biogenetic law to the 

 various groups of animals were also favorite subjects 

 of study. 



The most successful investigators in this period on the 

 different groups of animals include: Louis Agassiz on 

 the natural history and embryology of coelenterates and 

 turtles; A. Agassiz, embryology of echinoderms and 

 worms; H. J. Clark, embryology of turtles and syste- 

 matic papers on sponges and coelenterates; E. Desor, 

 echinoderms and embryology of worms; C. Girard, 

 embryology, worms, and reptiles; J. Leidy, protozoa, 

 coelenterates, worms, anatomy of mollusks ; W. 0. Ayres 

 and T. Lyman, natural history of echinoderms ; McCrady, 

 development of acalephs ; W. Stimpson, marine inverte- 

 brates ; A. E. Verrill, coelenterates, echinoderms, worms ; 

 A. Hyatt, evolutionary theories, bryozoa and mollusks; 

 Pourtales, deep sea fauna ; C. B. Adams, A. and W. G. 

 Binney, Brooks, Carpenter, Conrad, Ball, Jay, Lea, 

 S. Smith, Tryon, mollusks; E. S. Morse, brachiopods, 

 mollusks ; J. D. Dana, coelenterates and Crustacea ; Kirt- 



