744 THE GENERATIVE ORGANS. 
represented in the male Diptera, unless the penis and posterior 
gonapophyses are to be regarded as the ventral appendages of 
one or both these somites. I am inclined to regard the whole 
of the armature of the penis proper as the modified ventral 
appendages of the mesogenital somite, and as corresponding 
with the internal or posterior gonapophyses of Blatta. In the 
Hymenoptera the great hook-like internal gonapophyses are 
exceedingly similar to the paraphalli of the Blow-fly. It is 
possible, however, that the complex penis corresponds with its 
armature to two pairs of ventral appendages, those of the meso- 
and meta-genital somites. 
The Anal Somite (Fig. 106) is reduced to very small dimen- 
sions; it is tubular, and terminates behind in a pair of 
spathulate processes, one on either side of theanus. These are 
the valve interne already alluded to. They are covered with 
reflexed setze, and lie between the valvze externa. 
The Internal Valves (Fig. 106,7) lie one on each side of the 
anus, and dorsally to it. Each is moved by a strong apodeme ; 
they form a kind of canula as their ventral edges are united 
by a minute sclerite, which probably represents a sternal plate. 
I do not think that either the external or internal valves are 
true appendages, but believe both to be prolongations of the 
posterior edge of the terga of their respective segments. 
The Epipygium.—This term has been applied to the external 
and internal valves collectively. It is convenient, and I have 
already used it in this sense (p. 210).* 
* In the description of the abdominal skeleton (pp. 209, 210) I regarded 
the sternum, which I now term progenital, as the sternum of the seventh 
obvious tergum, a view which I have since rejected. This led to my re- 
garding the anterior gonapophyses as appendages of the seventh segment. 
In the description referred to the term seventh segment should, according 
to my present views, be read frogenital (eighth) segment, and the term 
ninth segment should be replaced by aval segment, which is theoretically 
the e/eventh, and not the ninth. 
