194 



THE COCKROACH : 



114, 115). From their backward-directed prolongations arises 

 the epithelium of the vasa deferentia and oviducts. All other 

 parts of the reproductive ducts are developed out of tegumen- 

 tary thickenings of the ventral surface in the last abdominal 

 segment, and the last but one. These thickenings are at first 

 paired,* but afterwards blend to form single organs (fig. 118). 

 Within the tegumentary thickenings just described, there 



D 



Figs. 116, 117, 118. Three stages of development of teguuieutary portion of Male 

 Sexual Organs of P. orientalis. (Oc. 1, Ob. B B, Zeiss.) V D, vas deferens ; 

 V S, vesicula seminalis ; D, ductus ejaculatorius ; P, p, penis and its lateral 

 appendages. 



appear in the male Cockroach two anterior closed cavities 

 which unite to form the single cavity of the permanent mush- 

 room-shaped body (vesicula seminalis). A. posterior cavity 

 becomes specialised as the ductus ejaculatorius, while the hind- 

 most part of the thickening, which is at first double, afterwards 

 by coalescence single, forms the penis (figs. 117, 118). The 



* This arrangement persists only in Ephemeridcv among Insects (Palmen, Ueb. 

 paarigen Ausfiihrungsgange der Geschlechtsorgane bei Insekten, 1884). 



