36 . Psyche [April- June 



margin of the ninth sternite where they are inserted in the hypo- 

 dermis. On page 47, he states that the penes (here homologized 

 with the penis valves "pv") arise as two protuberances of the 

 hypodermis in the location of the insertion of the vasa deferentia 

 {i. e. on the posterior margin of the ninth sternite), so that the 

 partially united appendages (labeled "pv" in Fig. 11) lying above 

 and between the gonopods "s," and forming the phallus or penis 

 of the male Blasturus may represent appendages of the ninth 

 segment in addition to the gonopods "s." If both penes and 

 gonopods are structures belonging to the ninth segment in such 

 primitive forms as the mayflies, this fact is of considerable impor- 

 tance in attempting to determine to what segment structures 

 homologous with them in the higher forms may be assigned; 

 and this also has some bearing on the view that the penis valves 

 "pv" represent the endopodites of a pair of abdominal limbs 

 whose exopodites are formed by the gonopods "s," since in order 

 to fulfil the latter conditions, both penis valves and gonopods 

 would have to belong to the same segment — for it is clearly impos- 

 sible for the exopodites of a pair of limbs to belong to one segment 

 while the endopodites of the same limb belong to another segment. 

 On the other hand, Wheeler, 1893 (p. 124) states that "the male 

 ducts of Blatta end at first in terminal ampullae enclosed by the 

 appendages of the tenth abdominal segment just as in Xiphidium" 

 but later "the terminal ampullae lie completely in the ninth seg- 

 ment, having shifted their position headward" (p. 118). On 

 page 132 he states that in Xiphidium and Blatta the male 

 ampullae lie "at the hind end of the ninth abdominal segment. 

 Just as the deferent ducts of ephemerids extend to the penes and 

 open to the exterior, so the terminal ampullae originally extend 

 into a pair of appendages, albeit on the tenth segment and not 

 opening to the exterior. If the penes of the ephemerids are really 

 modified ambulatory appendages they would be homologous with 

 the styli of Orthoptera. The curious persistence of these append- 

 ages in existing Orthoptera may be due to their having once 

 functioned as penes, long after the other abdominal ambulatory 

 appendages have disappeared." While I would not agree with 

 Wheeler in his suggestion that the penes of the ephemerids (which 

 are apparently homologous with those of the blattids) represent 

 the styli of the Orthoptera (i. e. that "pv" of Fig. 11 represent 



