THE MOVEMENTS OF COPEPODA. 507 



tionally, indeed, Copepoda seem to stand on pretty much the 

 same plane of development as the Protozocea larva. 



Phylogenetic hypotheses have too often been based on mere 

 resemblances in form, apart from a consideration of function. 

 This seems to me to be a wrong method of attacking the problem. 

 Function is the all-important thing — that which determines 

 structure; and I hold tliat if ever we are able to sift the primary 

 from the secondary elements in ontogeny, it will be by the recog- 

 nition of the fact that the persistence of ancestral structure is 

 caused by the retention of ancestral habits, and that the habits 

 at all periods of the life-history demand the closest study. 



Montreal; Oct. 15th, 1898. 



VOL. 42, PART 4. Nb;W SKKIES. 



M M 



