738 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 valve externze are a second pair of rod-like 
organs, which belong to the anal segment; these I term valve 
interne. The four valve are directed forward when at rest, 
and close the genital sinus, filling up the emargination in the 
fifth sternum. 
I'1c. 104.—A dorsal view of the progenital tergum of the male Blow-fly, showing the 
external and internal valves. e, external valve ; z, internal valves ; # m, muscles ; 
m, notch; 7”, rectum. 
The Dorsal Arches of the Sixth and Seventh Abdominal Annuli 
are very similar to each other; the former has two spiracles 
on each side near its posterior angle, and the latter only one. 
DescrIPTION OF PLATE LI, 
Side view of the penis of the Blow-fly. a, apodemes of the penis; 4, bulb; e, epi- 
pleural ridge ; gx, posterior gonapophysis 5 g's, genital sternum ; 4, hypophallus ; 
m m, muscles ; 0, orifice of the ejaculatory duct ; #/, paraphallus ; s, spine. 
