PROTECTIVE HABITS. 257 



tion we shall find that it has been the most important factor in evolution, 

 but that its importance as a conservator of species is due not to the tendency 

 usually attributed to it to preserve as many of the useful variations as pos- 

 sible, but to the fact that it holds the species, race, or variety to the modal 

 standard. So, too, it might with equal effectiveness be productive of the 

 development of varieties or of groups of species in highly variable forms 

 through this same strong tendency to segregate the species about one or more 

 conditions, and by the equally intense elimination of extreme or remote indi- 

 viduals. With any but the rabid selectionist it would go without comment 

 that the material must exist in such a state that selection can get a hold, or, in 

 other words, that the characters must have a selectional value either one way 

 or another before they can enter at all into the process. How these charac- 

 ters reach this state of development is a subject for experimentation and 

 research, and not for idle speculation. Finally, it has been seen that some 

 habits appear on first sight to be of great utility to the species, but are 

 not able to bear out this role when subjected to a broader and more careful 

 analysis. 



