46 THE UNIVERSITY SCIENCE BULLETIN. 



explains its function. It is undoubtedly used to coordinate 

 the action of the styles in copulation and usually also with 

 them, that of the oedagus. There are always more or less 

 prominent processes on the mesal margins of the styles to 

 which the connective is fastened. It varies much in the dif- 

 ferent genera being sometimes simply a transverse chitinous 

 bar, at other times it is U- or V-shaped, and often is quite 

 elongate and columnar in form. In rare cases it seems to have 

 no connection with the oedagus and is then much reduced 

 in size. The question of its homology seems to afford an 

 interesting problem for future work. 



The oedagus is commonly spoken of as the penis sheath. 

 In this cage ! ■ believe it ia the i»cnio i - tcolf and tho torms - ha ve 

 - been used synonymously. Professor Then called it the "Mem- 

 brum virile." It is also a chitinous sclerite, connected an- 

 teriorly with the connective. It assumes a great variety of 

 forms and is often very characteristic even in closely-related 

 species. Its base is usually quite enlarged or bears a more 

 or less strongly developed dorsally directed process. This is 

 for the purpose of fastening it to the wall of the genital cham- 

 ber which is composed of the membranes that form the anal 

 tube and the ental surfaces of the pygofers. The terminal 

 portion of the oedagus is variously developed, sometimes simply, 

 often with additional chitinous lateral or ventral processes. 



In addition to the above it has been found that the pygofers 

 themselves often bear chitinous bars or spines that are dis- 

 tinctive of the species. Thus the posterior margin of the 

 pygofers often bears a characteristic tooth or lobe, and in the 

 sides of these organs there are often characteristically shaped 

 chitinous structures. In some genera moreover the dorsal 

 margin bears chitinous bars which are specifically distinct 

 and which in some genera are united anteriorly, forming a 

 U- or V-shaped chitinous structure around the base of the 

 anal tube. These structures are, of course, too small for super- 

 ficial study, but because of being in the pygofers, are described, 

 when present, with the external genitalia. They seem to be 

 of equal importance in some cases with the internal genitalia 

 in the separation of species and varieties that show no differ- 

 ences in the external genitalia. 



It has been the purpose of this paper, to study and describe 

 these internal genitalia in representatives of the more import- 



