178 CALIFORNIA ACADEMY OF SCIENCES. 



It is bilobed, being divided by median dorsal and 

 ventral furrows into a right and left half. Each half is 

 again partially divided by a longitudinal furrow into 

 two secondary lobes, the outer of which is thinner 

 than the other. From the posterior end of the vesicle 

 a wide, almost straight ejaculatory duct passes to the 

 exterior. Its lower half is provided with a strong, 

 transverse musculature. The vasa deferentia appear to 

 open into the ejaculatory duct at a point above its mid- 

 dle. They, however, merely become attached to this 

 duct here, since they run forward along its sides, closely 

 bound to it, and enter the sperm vesicle. 



The vesicula seminalis of Trinoton luriduru is elon- 

 gated antero-posteriorly, tapers anteriorly, and is en- 

 larged and rounded posteriorly. From it the ejacu- 

 latory duct runs forward and to the left. Soon it makes 

 an abrupt bend backward and toward the middle line 

 again, where it enters a greatly enlarged and very 

 muscular division which opens to the exterior. 



The whole reproductive system of Menopon titan is 

 very greatly modified by an extreme complication of 

 the different parts. They are all essentially the same, 

 however, as in other species, and the modification is 

 mostly confined to the parts developed from the exterior 

 and to the muscles attached to these parts. These will 

 be described farther on. The main modification of the 

 inner organs is a great increase in the length of the 

 ductus ejaculatorius. The testes (plate xiii, fig. 10, t) 

 are oval, elongated tubes situated along the sides of the 

 body. The most anterior on each side is connected 

 with the anterior end of the vas deferens of the same 

 side. The second and third are connected with the same 

 duct at points farther back by rather long vasa effer- 

 entia. The part of the vas deferens between the first 



