510 P- E. Keuchenius, 



cula seminalis. The vesicula seminalis continues in the ductus 

 ejaculatorius, which opens into the sacculus ejaculatorius. 



The terminal part of the abdomen shows the same peculiar bend, 

 as we have already met with in the other Syrphidae treated, in con- 

 sequence of which the anus and genitalporus lie on the right side. 



The testes are not surrounded by f at-body-tissue. Their 

 Situation in the abdomen is variable. The right testis is always placed 

 more cranially than the left one. Both may be situated in the middle 

 or even in the left part of the abdomen. 



The testes are invested by the tunica externa and interna. 

 The tunica externa is an intensively brown pigmented layer with 

 large nuclei, surrounded by a clear protoplasm (fig. 16 n). Several times 

 I saw on the outside sections of tracheal trunks very close against 

 the externa. The tunica interna is developed in the distal part 

 of the testes as a flat epithelium, which proximally continues in the 

 membrana propria (fig. 16 m). In both specimens examined by 

 me, I saw a cellular ramified septum (fig. 16 sept) pushing into the 

 lumen of the testes. This septum connected two opposite walls of 

 the testes in an obliquely transversal direction. It is peculiar, that 

 on both sides of the septum, there is an excrescence to be seen (fig. 16 z). 

 In this excrescence I sometimes observed a vacuolar space, I do not 

 know the signification of this mysterious cell-excrescence. Perhaps 

 the study of the ontogeny of the testes may shed light on this question. 

 In the proximal part of the testes, I observed some cysts, and near 

 to it spermatozoa. The distal part is filled up with spermatozoa 

 and globular yolky elements, just like those I have discovered in Syrphiis 

 Ribesi (fig. 16 y). In the testes I also saw pointed oblong bodies, 

 in which no chromatin substances are to be seen. I have marked them 

 with X in fig. 16. These elements are perhaps degenerated sperma- 

 tids, but of course I am not sure of it. 



The tunica externa and interna continue unchanged on the 

 Short vasa deferentia, soon uniting into a caudally running un- 

 paired vas deferens (fig. IQu.vd). In transversal sections it appears, 

 that in fact both vasa deferentia continue independently. The 

 tunica externa becomes common for both, while the epithelium 

 tubes remain separated, just as we have observed in Syrphus, but with 

 this difference, that the partition wall between both epithelium tubes 

 IS also pigmented just like the whole common tunica externa (fig. 17). 



'The accessorial tubes have no windings, at the most they 

 are bent a little (fig. 15 acc). Near their end they run, parallel with 



I 



