REPRODUCTION. 



177 



Subsequently the enlarged heads disappear. The spermatozoa 

 move actively. In adult males the testes undergo atrophy, 

 but can with care be discovered in the enveloping fat-body. 



The vasa deferentia are about "25 inch in length. They pass 

 backwards from the testes, then turn downwards on each side 

 of the large intestine, and finally curve upwards and forwards, 

 entering the vesiculae seminales on their dorsal side. Each vas 

 deferens divides once or twice into branches, which immediately 

 reunite ; in the last larval stage the termination of the passage 

 dilates into a rounded, transparent vesicle. 



Fig. 100. Male Organs, side view. T~ , seventh tergum ; S~ , seventh sternum; 

 Ts, DE, as before. A, E, see fig. 102. X 8. 



The vesiculse seminales are simple, rounded lobes in the 

 pupa (fig. 101), but their appearance is greatly altered in the 

 adult by the development of two sets of utricles (modified 

 accessory glands). The longer utricles (utricnli majores) open 

 separately into the sides of the vesiculee ; nearer to the middle 

 line are the shorter and more numerous utriculi breviores, which 

 open into the fore part of the vesiculse. 



The utricles form the " mushroom-shaped gland" of Huxley, 

 which was long described as the test-is. In the adult male the 

 utricles are usually distended with spermatozoa, and of a 

 brilliant opaque white. 



