1918] Morphology of Genitalia of Insects 117 



forms to obscure the ventral view of the somites. After the 

 time of hatching, Wheeler calls attention to the fact that Dewitz, 

 in 1875, traced the development of the ovipositor in another 

 locustid, Locusta viridissima, so that we now have the complete 

 history of that organ, or set of organs. Wheeler concluded that 

 part of his account as follows: "While there can be no doubt 

 about the appendages of the eighth and ninth segments which 

 go to form the two outer sheaths of the ovipositor or sting, the 

 development of the innermost blades is by no means so satis- 

 factory. But whether this pair is only a portion of the ninth 

 pair of appendages as most authors claim, or represents the 

 tenth pair as I maintain, the main question at issue is in no wise 

 affected ; for it still remains true that the ovipositor consists of 

 two or three pairs of modified ambulatory limbs." In the male 

 Xiphidium embryo, it is claimed by Wheeler that the pair of 

 appendages on the ninth somite persists, to form the definitive 

 styli, those of the eighth and tenth somites disappearing very 

 early. To quote again, "The continuity of the sjcyli" — meaning 

 here male genitalia — "with the embryonic appendages was 

 quite as satisfactorily observed as the continuity of the ovi- 

 positor blades." He also says of the investigations of others, 

 " Cholodkovsky has made an exactly similar observation on 

 Blatta." The styli, therefore, in the male "are the homologues 

 of the second pair of gonapophyses " in the female. " Haase 

 must, therefore, have gone astray in seeking to homologize the 

 styli" in the male, "with the styloid processes or 'Griff el'" 

 above-mentioned in this paper as those styles attached to the 

 coxae of certain of the abdominal somites of some Thysanura, 

 "for the styli," concludes Wheeler on the male Xiphidium, "are 

 modified ambulatory appendages." 



5. Cerci. — One more pair of appendages, namely, the cerci, 

 should properly be included under the term genitalia, making 

 the total number four pairs. The cerci, often tactile in function 

 when present, are frequently described as attached to the ter- 

 minal or anal somite. That different investigators have not 

 meant the same thing, morphologically, by cerci, is undoubtedly 

 true. Some regard them, not as appendages, but as prolonga- 

 tions of pleurites, i. c, of epimerites and episternites. Berlese 

 explains this point of view, which he apparently takes. He says 

 that there may be cerci on the tenth somite, as also on the ninth, 

 the presence of the one generally excluding that of the other. 



