180 CALIFORNIA ACADEMY OF SCIENCES. 



line to its posterior end, where it becomes narrower 

 and turns toward the middle line. It reaches the trans- 

 verse muscles of the penis and becomes here thrown 

 into several loops, and then runs forward among 

 the longitudinal muscles of the penis to the anterior 

 end of the innermost {int) tube of the latter, with 

 which it becomes continuous. 



Nitzsch does not describe extensively the repro- 

 ductive organs, merely giving a general description of 

 them for the different suborders. He figures, however, 

 the male organs of Colpocephalum fiavescens and of Men- 

 opon pallidum. In the former (plate xiii, fig. 7) the six 

 testes (t) are pear-shaped, situated with their broad ends 

 upon the vasa deferentia (vd), with which they are con- 

 nected by very short secondary ducts. Their pointed 

 ends are terminated each by a short fiber. The vasa 

 deferentia run backward and inward, uniting with the 

 basal portion of the ductus ejaculatorius (ej) far from 

 the vesicula seminalis (sv). The latter is somewhat 

 elongated divided longitudinally to near its base by a 

 median and two lateral grooves. The ejaculatory duct 

 is very long. Immediately after leaving the vesicula 

 seminalis it turns forward lateral of this organ and 

 runs forward to some distance beyond its anterior end; 

 the duct then turns backward and slightly inward, end- 

 ing in a somewhat enlarged basal part to which is 

 attached an internal chitin rod (r). In this form and 

 in Physostomum diffusuDi the ductus ejaculatorius is very 

 wide compared with this duct in Menopon titan and 

 Menopon pallidum. In Physostomum it is provided 

 with very prominent transverse muscle fibers. 



In Menopon pallidum., as figured by Nitzsch, the testes 

 are small, oval, and connected with the vasa deferentia 

 by rather long ducts. The vasa deferentia are much 



