History of Comparative Anatomy 351 



(Harvard Medical School), C. O. Whitman (University of Chicago), 

 and Edmund B. Wilson (Columbia University). 



In Paleontology, Cuvier's pioneering work was carried forward 

 by Louis Agassiz who studied the European fossil fishes in Cuvier's 

 great collection in Paris and published (1833-44) a three-volume mono- 

 graph on them. The brilliant work of Charles Lyell (1797-1875) in 

 England, primarily geologic, but having highly important bearings on 

 the interpretation of fossils, was followed by that of Owen and Huxley, 

 already mentioned, while in Germany the leader was Karl von Zittel 

 (1839-1904). In America, three men, Joseph Leidy (1823-91), E. D. 

 Cope (1840-97), and O. C. Marsh (1831-99), devoted their lives to 

 exploration of the extraordinarily rich deposits of fossils in the western 

 United States. A little later, notable contributions to vertebrate pale- 

 ontology, both factual and theoretic, were made by Henry F. Osborn 

 (1857-1935), long associated with The American Museum of Natural 

 History in New York City. 



TWENTIETH-CENTURY CAUSAL MORPHOLOGY 



In the last decade of the nineteenth century, Biology stood at the 

 threshold of a new epoch. Evolution was no longer an issue. To most 

 scientific minds it had become an accepted fact. Biologic knowledge 

 had been rearranged and set in order on the evolutionary basis. But it 

 is not to be inferred that nothing was left for Comparative Morphology 

 to do. While the main lines of the evolutionary picture seemed clearly 

 discernible, a vast number of intricate pieces of the picture puzzle re- 

 mained to be fitted into place. For Anatomy, there were obscure and 

 poorly understood organs, and numerous animals which had never been 

 fully studied. In Embryology, only a comparatively few conveniently 

 available or supposedly representative animals had been thoroughly 

 studied, and every stage of development presented problems. Paleon- 

 tology had little more than scratched the surface. While the main 

 trunks of genealogic trees seemed safe enough, many branches were 

 admittedly shaky and the arrangement of the smaller twigs was being 

 changed daily. For anyone inclined toward morphologic work, there 

 was no lack of things to be done, and that still holds true. 



But some scientific minds are like an explorer who, having dis- 

 covered a country, is not content to settle there but must push on in 

 the attempt to discover another. Evolution had been "discovered" and 

 so the more restless minds, accepting evolution as an established fact, 

 began to push into new territory. The causal factors in evolution were 

 still subject to as much doubt and disagreement as ever. "Inheritance 

 of acquired characters" had not been proved. "Natural selection" had 

 been judged inadequate to account for all of evolution. Weismann 



