744 THE GENERATIVE ORC.AXS. 



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 the anus. These are 

 the valvae internee already alluded to. They are covered with 

 reflexed setae, and lie between the valvae externae. 



The Internal Valves (Fig. 106, z) 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 terguin, 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 prvgenital (eighth} segment, and the term 

 ninth segment should be replaced by anal segment, which is theoretically 

 the eleventh, and not the ninth. 



