1918] Morphology of Genitalia of Insects 123 



here that Heymons makes his best point in regard to the 

 homologies between styles and genitalia, but in these forms 

 both styles and appendages are often attached to the same 

 somites. A careful survey, however, of Figure 12 (Plate IV) of 

 the more generalized female shows that the latter are important 

 outgrowths, which so far as the adults are concerned, may far 

 better be considered genitalia than styles. In the embryos 

 figured by Heymons the buds, anlages of genitalia and styles, 

 are so near together as to be easily confused and to give ground 

 for the belief that they are one and the same thing, not separate 

 from the very beginning. On the other hand, this separation 

 shows very clearly in his figures, even in those of insects which 

 have entirely degenerate styles ; that is, none, in the adult. He, 

 however, does not interpret his figures nor yet his material in 

 that way. He considers that the appendages found in the adult 

 are simply the . final specialization of these same above- 

 mentioned styles. 



In the male and female Lepisma (Plate IV, Figs. (3, 7, 10, and 

 12), again it is evident that in the adult insect there are appen- 

 dages corresponding to Appendage I as well as styles, on the 

 same somite, and it seems unnecessary to correlate those 

 appendages found on the terminal somite of Lepisma and 

 Machilis with styles when they resemble so closely certain 

 appendages, cerci or Appendage IV, of similar form in many 

 groups where styles are not present. It should be said in this 

 connection that the terminal median appendage present in the 

 Lepisma and shown in the figures of that insect is the one 

 which, including also the anal lobes, Heymons and Uzel 

 homologize with the eleventh somite. 



Table oi" Sclerites and Appendages. 



SOMITES 



Lepisma saccharina 7, 8, 9, 10. 11. 



Female t+ t+ t+ t+ t + 



s+ 8+ s+ 8+ si- 

 Male t+ t+ 1+ t+ t+ 



s+ s+ .s+ s+ s+ 

 Machilis sp. 



Female t+ t+ t+ t+ t-|- 



s+ s+ s+ s-f s+ 



Male t-\- t+ t+ t+ t-f- 



s-i- s+ s+ s+ .s+ 



