LEE BARKER WALTON 11 



on the subject under discussion, beyond indicating that in 

 using the term "primitive metamere" we must not exclude 

 the idea that such a metamere may in turn represent a 

 fusion of an indefinite number of annuH. Evidence is 

 thus added to a segment-fusion theory rather than to the 

 biramose theory. 



While it appears possible that the exopodite and ento- 

 podite in Crustacea may have developed from dorsal and 

 ventral parapodia, in direct contrast to the manner in- 

 dicated above for the Chilopoda and Hexapoda, further 

 study may show a common origin of the two processes. 



Summary 



In Hexapoda and Chilopoda the "coxa" is composed of 

 two more or less fused segments, coxa gemiina and meron. 



The antecoxal piece results from the chitinization of 

 the membrane connecting the coxa with the sternum. 



The trochantin probably originated from a lateral por- 

 tion of the same membrane. 



Audouin erroneously homologized the lateral margin 

 of the posterior coxa in Dytiscus circumflexiis with the 

 trochantin of the prothorax and mesothorax. 



The trochanter represents a distinct segment of the legs. 



The meron and coxa genuina, together with their cor- 

 responding basal segments epimeron and episternum, give 

 evidence of a fusion between two primary metameres in 

 the Hexapoda and Chilopoda. 



In Hexapoda and Chilopoda the anterior metamere 

 bears the functional, and the posterior, the rudimentary 

 leg. 



Of the primitive Hexapoda, Neuroptera [Planipennia] 

 exhibit the most generalized condition in the development 

 of the coxa, while in Thysanura and Orthoptera a high 

 degree of speciahzation is shown. 



