568 THE EVOLUTION OF LIFE. 



of species-marks are formed out of inanimate tissue or tissue 

 of low vitality tissue which, like hair, feathers, horns, teeth, 

 is composed of by-products unfit for carrying on vital 

 actions. 



174e. In the days when, not having been better in- 

 structed by Mr. Darwin, I believed that all changes of struc- 

 ture in organisms result from changes of function, I held 

 that the cause of such changes of function is migration. As- 

 suming as the antecedent of migration a great geologic 

 change, such as upheaval of the East Indian Archipelago 

 step by step into a continent, it was argued, in an essay I 

 then wrote, that, subjected primarily to new influences in its 

 original habitat, each kind of plant and animal would sec- 

 ondarily be subjected to the altered conditions consequent 

 on spreading over the upheaved regions. 



"Each species being distributed over an area of some extent, and 

 tending continually to colonize the new area exposed, its different 

 members would be subject to different sets of changes. Plants and 

 animals spreading towards the equator would not be affected in the 

 same way with others spreading from it. Those spreading towards 

 the new shores would undergo changes unlike the changes undergone 

 by those spreading into the mountains. Thus, each original race of 

 organisms would become the root from which diverged several races 

 differing more or less from it and from one another." 



It was further argued that, beyond modifications caused by 

 change of physical conditions and food, others would be caused 

 by contact of the Flora and Fauna of each island with the 

 Floras and Faunas of other islands: bringing experience of 

 animals and plants before unknown.* 



While this conception was wrong in so far as it ascribed 

 the production of new species entirely to inheritance of 

 functionally -wrought alterations (thus failing to recognize 

 Natural Selection, which was not yet enunciated), it was right 

 in so far as it ascribed organic changes to changes of condi- 

 tions. And it was, I think, also right in so far as it implied 

 * Westminster Review, April, 1857. "Progress: its Law and Cause." See 

 also Essays, vol. i. 



