Pairing of the Plebeiid Blue Butterflies. 163 



(vesica, Pierce) and the more internal portion which is 

 never everted. 



In some species with longer external portions to the 

 aedeagus (as in Thecla) there is, strictly speaking, no 

 eversible membrane, the extremity of the aedeagus appears 

 to reach the bursa and there expands, by the spreading 



Fig. 5. — A diagram to show the continuity of the azygos duct 

 with the cutaneous surface (floor of genital cavity). The 

 arrows indicate the route from the external surface by way 

 of the membranous sheath (sinus*), the surface so far, often 

 bearing hairs, to the zone, thence, fused to its returning layer, 

 to the internal opening of the aedeagus and back again, con- 

 tinuing then as the external portion of the shaft of the aedeagus, 

 and at its extremity returning as eversible membrane and 

 ductus. 



of portions of its extremity and stretching of the adjacent 

 membrane; this membrane and the movable portions at 

 the extremity of the aedeagus are, however, no doubt, 

 homologous with the eversible membrane and cuneus 

 (cor nidi, Pierce). 



* Zander, Zeitsh. fur. Wiss. Zool. 1903, applies the term penis- 

 lasche to the sleeve for which I have accepted the name sinus, but 

 extends the said penis-lasche not only to the base of the aedeagus 

 but right away beyond the aedeagus along the ductus ejaculatorius, 

 where it is quite five from the aedeagus in the abdominal cavity. 

 He uses rinywall for the ar mature that often surrounds the aedeagus 

 nn the Moor of the genital cavity (diaphragm), and which other 

 authorities call jjenis-tasche. 



M 2 



