528 P- E. Keuchenius, 



Consequently I strongly doubt, if this blind sack serves as vesicula 

 seminalis and if this name is justified here, though its Situation 

 would seem to suggest as miich. I suppose the vesicula seminalis 

 to be an accessorial gland, wliich belps in producing the fluids for 

 liquifying and thinning the sperm. The vesicula seminalis narrows 

 caudally and continues in the veiy short ductus ejaculatorius 

 (fig. 68 d.ej), which opens to the outside by means of a chitinous canal. 

 This canal (fig. 68 d.cop) is not surrounded by a layer of cells and is 

 at its commencement provided with a widening (fig. 68 sac) in the 

 form of a sack. This sack I would identify with the sacculus eja- 

 culatorius. An apothetes ejaculatorius is not to be found in 

 this species. 



General summary and conclusions. 



In the first place I would refer to the asymmetrical position of 

 the testes. This asymmetry is not to be seen in the objects, which 

 are sectioned out of the abdomen, but only in the microtomical sections 

 and therefore it is not to be observed either in the diagrams which I 

 have given. Brüel was the first to discover this asymmetry in Calli- 

 fliora erythrocephala (2, p. 513) whilst Cholodkovsky (3) and Hewitt (9) 

 do not mention it. I observed it in all the Diptera examined by me, 

 and besides I generally found the right testjs placed more cranially 

 than the left, while also the asymmetry was sometimes more strongly 

 marked {Leptis) and sometimes less. With Pollenia and Musca a very 

 rare case happened, to wit that the left testis was situated more cra- 

 nially than the right. Also in relation to the gut, the place of the 

 testes is mostly non-symmetrical and very changeable. So I some- 

 times found in a few Diptera (Leptis), the right testis more dorsally 

 placed than the left one and in other species [Syrphus Ribesi) just 

 the contrary, whilst in most species {Leptis, Pollenia, Lucilia, Sarco- 

 phaga, Dexia, Tipula, Musca) they are situated ventro-laterally of 

 the gut. In RJiingia rostrata both testes are sometimes found entirely 

 in the left half of the abdomen and in Leptis on the other band in the 

 right. As a matter of course this position of the testes refers to the 

 caudal part of the intestine, the testes, too, being situated caudally 

 in the abdomen, and the more cranial part moreover being twisted. 

 In all the Syrphidae examined by me, I saw a peculiar bend of the 

 end of the abdomen going to the right side in a cranial direction. 

 DuFOUR had perceived this peculiarity in Volucella zonaria and said 

 of it, that it is: "dans l'etat de repos ploye et regu dans une excava- 



