( cxxii ) 



venter, the sedoeagus is moderately long and straightisli ; on 

 each side of it there is a gonapophysis with a large ample 

 basal joint, at the end of which a long gradually tapering 

 somite is articulated, whilst through both of these a long sensory 

 duct is discernible terminating in a fine stylet emitted from 

 the tapered end of the somite just referred to. 



Petrobius brevistylis, Carpenter, 



has the sedoeagus very long, of moderate width for its basal 

 half, when it gradually expands, and is roughly the shape of 

 an Indian club; its enveloping case is simple, only covering 

 half the length, but in addition there are a pair of rather 

 longer somewhat narrowly elliptical sclerites, forming a 

 vertical cover to the basal part of the sedoeagus. The gonapo- 

 physes (one on each side) have the basal somite less ample 

 than in niaritimus, whilst the terminal somite is shorter but 

 more robust and almost straight, with a bluntly rounded apex, 

 from which is emitted the very short stylet that forms the end 

 of the long sensory ducts running through these organs. I 

 believe that this whole group of insects has the male organs 

 developed on similar lines to these. 



In the Orthoptera the genitalia have been used in recent 

 years with much advantage for classificatory pm-poses. In 

 the Dermaptera the word " parameres " has been adopted 

 for parts of the armature that are apparently more or less 

 homologous to some of the clasping organs in other orders. 

 Zacher and Burr and Jordan have all dealt with the repro- 

 ductive organs including these parts, and as Dr. Burr has 

 ready a valuable work on the subject it is unnecessary to touch 

 on it here. I may, however, present a single figure of another 

 section of the order, viz. the cockroaches. Blatta and Peri- 

 planeta follow closely similar lines; both have thoroughly 

 asymmetrical organs though they differ in certain minoi- 

 cliaracters. 



Periplaneta americana 



has a pair of large outer cerci in which the asymmetry 

 referred to is very evident : the length of the one differs from 

 that of the other, the articulations differ also, both in number 



