The structure of the internal Genitalia of some male Diptera. 519 



from the epithelium and pushing into the limien of the testes, but I 

 will not deny the possibility of their presence. Against the lining 

 of the testes, we can discern in the lumen, going proximo-distally 

 a layer composed respectively of gonocysts, cytocysts and sper- 

 matocysts (fig. 38, g.c, cy.c, sp.c), while in the bhnd cranial apex 

 nearly exclusively gonocysts and cytocysts are present. In the 

 Contents remaining, bundles of ripe spermatozoa (fig. 38 s^^) are to 

 be found and between them degenerated cysts (fig. 38 deg.c) and 

 yolky or cellular bodies (fig. 38 y) derived from the contents of those 

 degenerated cysts. Quite caudally in the lumen of the testes ripe 

 spermatozoa are chiefly to be seen. It is a matter of course that 

 mitotical division-figures in those different cysts are to be observed. 

 \Ve have already remarked where the continuation of the testes into 

 the vasa deferentia is to be found. 



In several bends these vasa deferentia run to their ending 

 into the ductus ejaculatorius. The investments of the vasa 

 deferentia (fig. 41) are an immediate continuation of the coverings 

 of the testes. The pigmentation of the tunica externa (fig. 41 ex) 

 however continues only a short way on the vasa deferentia. 



The two accessorial glands are tubes, bent many times, which, 

 it seems, are much longer and voluminous in older specimens. The 

 outer investment is thin (fig. 42, Ä and B, ex) and provided with small 

 nuclei. It gets less intensively stained than the lining (fig. 42, A and 

 B, in) of the glands. The structure of the lining epithelium differs 

 at the beginning (fig. 42/1) to that near the end (fig. 42 B) of the 

 accessorial glands. Here, where the tube is narrower, the epithelium 

 folds, so that the lumen becomes very irregulär; this is not the case 

 at the commencement of the gland-tubes. It is stränge, that here 

 also the epithelium, which is of course a gland-epithelium, should not 

 give the Impression of being such, because it appears, especially at 

 the commencement of the tubes, as a rather flat epithelium (fig. 42, 

 Ä, in). Without doubt the cells have secreted in younger periods and 

 this is to be observed in the lumen of the tubes, which is filled up 

 with the weak colouring secreta, whilst now they have lost their secret- 

 ing function. 



The vasa deferentia and accessorial gland-tubes join on a 

 common papilla, where they open into the ductus ejaculatorius. 

 Each of the tubes, however, remains independently, so that each of 

 them has its own orifice (fig. 44 vd and acc) on the papilla. 



The ductus ejaculatorius, which begins with this papilla is 



34* 



