NEW MAr.I.OI'HAtiA. l!'l 



part of the penis. The several processes serve, liow- 

 ever, partly for tiie attachinont of muscles. The ante- 

 rior half of the internal ])late is comparatively very thin 

 and tapers to a blunt termination in front. Back of 

 the niidtile, also, the plate contracts somewhat toward 

 its base. The external penis has a large, thick, basal 

 part, which rapidly contracts to a slender, tubular, dis- 

 tal })art, terminating by an arrowhead-shaped enlarge- 

 ment, the posterior angles of which are very sharp. 

 This terminal tube curves downward a little toward its 

 tip (plate XV, fig. 1), where its inner cavity opens to 

 the exterior. 



To the anterior end of the chitinous penis on its 

 ventral side are attached two wide sets of muscle libers. 

 These pass backward, outward, and a little ventraliy to 

 the ventral wall of the abdomen. Each set is parallel- 

 sided and arises from the penis just to one side of the 

 middle line, and as the two diverge backwards they 

 form onlv a verv small any;le with each other. To the 

 other end of the penis are attached four sets of muscles, 

 two dorsal and one on each side. Each lateral bundle 

 is attached to one side of the enlarged subterminal part 

 of the penis. It passes forward and outward, forming 

 an angle of about 45° with the penis, to the lateral 

 wall of the body-cavity. The dorsal muscles are near 

 the middle line, and extend anteriorly, outward, and 

 dorsally. These posterior sets are shorter than tlie 

 anterior ones, endins; on the bodv walls in the fourth 

 and fifth segments. 



The mechanism of the chitinous parts, invaginated 

 tube, and muscles is self-apparent. The anterior 

 muscles contracting push the chitinous penis backward, 

 and it carries outward the partly evaginated inner tube 

 of the genital cavitv, the flexible walls of which become 



