458 The American Naturalist. [June, 



than in the domain of his higher faculties, for the reason that 

 Selection may operate upon variations in mind, while it taxes 

 our credulity to believe it can operate upon variations in 

 muscle and bone. This is my ground for selecting the skele- 

 ton and muscles for the subject of the introductory lecture. 

 Nevertheless, let us review variation in all its forms in human 

 anatomy before forming an opinion. Let us remember, too, 

 that congenital and acquired variations are universal as neces- 

 sities of birth and life ; they are exhibited in the body as a 

 whole — in its proportions, in the components of each limb, 

 finally in the separate parts of each component, as in the 

 divisions of a complex muscle. Thus the possibilities of 

 transformism are everywhere. What is the nature and origin 

 of congenital variations? Their causes? Do they follow cer- 

 tain directions ? Do they spring from acquired variations by 

 heredity ? These are some of the questions which are still 

 unsettled. 



But striking as are the anomalies from type, the repetitions 

 of type as exhibited in atavism and normal inheritance are 

 still more so, and equally difficult to explain. Therefore our 

 theory must provide both for the observed laws of repetition 

 of ancestral form and the laws of variation from ancestral 

 form, as the pasture-land of evolution. Add to these, that for 

 a period in each generation this entire legislation of nature is 

 compressed into the tiny nucleus of the fertilized ovum, and 

 the whole problem rises before us in the apparent impregna- 

 bility which only intensifies our ardor of research. 



The anthropologists and anatomists have enjoyed a certain 

 monopoly of Homo sapiens, while the biologists have directed 

 their energies mainly upon the lower creation. But under the 

 inspiring influences of the Darwinian theory these originally 

 distinct branches have converged, and as man takes his place 

 in the zoological svstein. comparative anatomy is recognized 

 as the infallible key to human anatomy. 



For our present purpose we must suppress our sentiment at 

 the outset and state plainly that the only interpretation of our 

 bodily structure lies in the theory of our descent from some 

 early member of the primates, such as may have given rise 



