NEW MALLOPHAr.A. 189 



organ. The opening of the alimentary canal into it is 

 ajtparently a secondary resuh, since tlie anus is 

 terminal and exposed in the female wlien the genital 

 cavity is in front of the, last sternum. 



Longitudinal sections through the male show that 

 the genital cavity is formed by a wide invagination of 

 the hind end of the abdomen (plate xv, lig. 1). The 

 cavity is almost as wide as the body itself, and extends 

 from the posterior border of the last segment far into the 

 eighth. In its upper wall near the posterior margin is 

 the anal opening ((0- From its inner end an evagina- 

 tion of much smaller diameter than the primary invag- 

 ination takes place, forming a long, rather slender, dis- 

 tally tapering tube in whose walls a thick deposit of 

 chitin is present. This is the penis {j>). From its base a 

 large, wide chitinous plate extends forward v:ithin the 

 body-cavity {pi). The part of the penis lying within the 

 genital cavity will be spoken of as the external part of 

 the penis, and the plate extending forward within tiie 

 body cavity as the internal part. It is to be noted, 

 however, thai the plate is strictly external, since it is 

 simply a part of the chitinous covering of the body, 

 and that it is internal only in the sense that an inward- 

 running process of the body-wall is internal. The gen- 

 ital chamber reaches much farther forward below the 

 penis than above it. At the point where the internal 

 and external parts of the penis are continuous, the duc- 

 tus ejaculatorius (ej) enters into tiie evagination of 

 which the outer part is formed, and opens by a termi- 

 nal orifice to the exterior. The internal plate extends 

 forward beneath the ductus ejaculatorius and close to 

 the ventral wall of the body to the anterior border of 

 the second abdominal segment. To it the muscles {em) 

 of the penis are attached. 



