The structure of the internal Genitalia of some male Diptera. 525 



vasa deferentia begin at the caudal apex of the testes and rim 

 at first caiidally, without being twisted (fig. 55 vd). Their lumen is 

 filled up with spermatozoa. Suddenly the vasa deferentia swell 

 in the form of a bladder (fig. 55). The walls of this bladder are com- 

 posed of two layers, because here I could observe very small flat nuclei 

 on the outside (fig. 57 ex). It is pecuHar, that these bladders and 

 also the vasa deferentia in their fiirther course are surrounded by 

 a covering, which is formed by a fat-tissue, that has the thickness 

 of one or two cells and which I call the tunica adipo-membranacea. 

 This tunica was already discovered by DurouR (6, p. 217). It, however, 

 surrounds very loosely the organs, which lie in it (fig. 58 t.ad.m). The 

 Contents of the bladder (fig. 57) consist of spermatozoa (sp), which 

 appeared to me to float in a fluid. In the bladder I saw cellular septa 

 going out from the epithelium. I do not know the meaning of these 

 septa. The bladder seems to function as a kind of temporary deposi- 

 tory of spermatozoa. Probably, however, it also may have had a 

 secreting function during the larva-stage, and this suspicion increases 

 when we compare the next species to be described. The vasa de- 

 ferentia [i\g,'6bvd) continue after passing through the bladder, in 

 a caudal direction and then they are more voluminous. Soon the 

 left and right vas deferens meet with each other and from this 

 moment, whilst making a spiral winding, they run parallel and very 

 close to each other (fig. 55), The Contents of the vasa deferentia, 

 after their passing through the bladdery swelling, are composed of 

 spermatozoa (fig. 58 sp), whilst also the tunica adipo-mem- 

 branacea (fig. 58 i.aflt.m) keeps surrounding each separately. 



The accessorial tubes are two long and many times twisted 

 tubes, also loosely surroimded by the tunica adipo-membranacea 

 (fig. 55 acc and fig. 59). The gland -tubes are invested by two layers; 

 on the outside by the very thin tunica externa (fig. 59 ex), which 

 sometimes tears off from the lining epithelium. This, is a high co- 

 lumnar gland-epithelium, the cells of which are separated by very 

 distinct intercellular fissures (fig. 59 in). 



Near their end, the accessorial gland -tubes become narrower 

 and open, together with the vasa deferentia, on a common papilla 

 at the cranial side of a bladdery widening (fig. 55), which forms the 

 commencement of the ductus ejaculatorius (fig. 55 d^.e;). Each 

 tube has its own orifice on the papilla. This bladdery widening of the 

 ductus ejaculatorius is a gland, as is proved by the very high 

 columnar epithelium (fig. 60) by which it is lined. The cells of this 



