1922] Walker: Structure of Orthopteroid Insects 45 



one of these genera, consisting of an eversible hook, whose 

 sheath forms an irregular membranous prominence which is 

 continued sinistrad with a long membranous fold under the 

 paraprocts to the corresponding dextral prominence. The 

 latter is much sm.aller and bears an irregularly folded structure 

 with chitinous edges, which in general appearance is suggestive 

 of the dextral paramere of Parcoblatta, but which is probably 

 more nearly comparable to the sinistral structure of Periplaneta 

 in a very aborted condition. 



In this species is seen something of the tendency met with 

 in Blatta, Periplaveta, the Mantidce and Grylloblatta of the 

 dextral paramere (or paramere-bearing outgrowth) to overlap 

 the sinistral one. 



PERiPLA>yErA. In this genus the paraprocts are symmetrical 

 but the genitalia are strongly asymmetrical and exceedingly 

 complicated. The paraprocts are dorsall}^ but little chitinized, 

 but are covered ventraily by large plates, which are separated 

 only by the anal fissure, and simulate closely a divided sternum. 

 They are without the hooks met with in the other forms 

 described. 



The paramere lobes are both large and prominent, par- 

 ticularly the sinistral, and are separated by a very oblique 

 fissure, from which a large fleshy lobe representing the penis 

 (the "lame mediane" of Peytoureau, '95)* emerges below and 

 is directed obliquely dextrad. The wide ejaculatory duct 

 opens upon its membranous dorsal surface, near the apex. 

 The ventral surface is somewhat chitinized. 



The three species of Periplaneta examined difi^er greath^ in 

 the details of the genitalia, but agree in general structure. 



The dextral paramere is fundamentally similar to that of 

 Blattella, but is much m.ore comiplex and its parts more heavily 

 chitinized. In P. juliginosa Serv. the basal apophysis is short 

 and broad, and concave on its inner face. The shaft is an 

 irregular, curved sclerite, divided into proximal and distal parts, 

 the former strongly folded and articulating with the apophysis 

 with which it is connected by muscles. The distal part is 

 bifurcate, the upper branch short and terminating in several 

 irregular teeth, the lower long and slender and tapering to a 

 point. The chitinized inner fold of Blattella and Parcoblatta is 



* The process termed the penis by Peytoureau is a part of the sinistral lobe. 

 Peytoureau, however, observed correctly the position of the genital aperture. 



