73 8 THE GENERATIVE ORGANS. 



integument. A notch is seen in front at the base of each, 

 which is suggestive of an articulation with an appendage, but 

 no such appendage exists (Fig. 104). 



Between the valvse externae are a second pair of rod-like 

 organs, which belong to the anal segment ; these I term valvae 

 internee. The four valvae are directed forward when at rest, 

 and close the genital sinus, filling up the emargination in the 

 fifth sternum. 



I I'.. 104. A dorsal view of the progenital u-rquni of the male Blow-fly, showing the 

 external and internalValves. e, external valve ; /', internal valves ; in m, muscles ; 

 , notch ; r, rectum. 



The Dorsal Arches of the Sixth and Seventh Abdominal Annul! 

 are vtry similar to each other; the former has two spiracles 

 on each side near its posterior angle, and the latter only one. 



I i, .kill II.N ..I I'l.Al I. I.I. 



Side view of the pi-ni* <>( the I'.low-fly. <7, apndeines of the penis ; !', bull) ; t, epi- 

 ].;> ural rii'n' : posterior gonapoph] . , genital fcternum ; A/, hypophallus ; 



in in, muscles ; u, unii> c "I ilie i-jaculatory duct ; //, paraphallttS ; s, spine. 



