26 



PROCEEDINGS OF THE NATIONAL MUSEUM 



that identification of a male specimen as a Cleptoria can be made 

 with the unaided e3 r e. As implied by its name, C. divergens has a 

 somewhat less characteristic gonopod and rather approximates 

 a structure one might consider as fairly typical of Sigmoria. Perhaps 

 this species represents a level of evolution just beyond that of the 

 dichotomy separating the stocks ancestral to present members of 

 these two genera. Certain species of Cleptoria appear to be closely 

 related in the gonopod structure as indicated by the very provisional 



BIPRAESIDENS "P^C 1 



Figure 23. — Superposition of phylogenetic dendrogram from figure 22 upon the known 

 distribution of species of Cleptoria. 



diagram in figure 22. The overall appearance of the appendage is 

 judged in guessing at affinities and not single "key-characters" that, 

 although obvious, probably have little significance in phylogenesis. 

 The presence or absence of a prefemoral process, for instance, con- 

 stitutes such a character. 



By the assumption that the gonopod of C. divergens represents a 

 relatively unspecialized form, it is possible to arrange the species of 

 Cleptoria in a tentative evolutionary sequence with C. abbotti repre- 

 senting the extreme development: its gonopod is especially shortened 



