The structure of the internal Genitalia of some male Diptera. 515 



suddenly (fig. 27) loses its cellular character and is developed over 

 the whole lining of the testes as a membrana propria. At the 

 place, where we can see the continuation of the epithelium in the 

 membrana propria, a cellular septum pushes into the lumen of 

 the testes (fig. 27 sept). We must suppose, that here a transversal 

 ringlike pleat is formed at the distal apex of the testes by the epithe- 

 lium. The lumen of the testes consists of different transition-stages 

 of the development of the germ-cells and again the younger stages 

 are seen proximally and the older distally. Quite ripe spermatozoa 

 (fig. 27 sp) are to be found only in the axis of the proximal part. Be- 

 tween them I saw romid cysts, containing cellular bodifes (fig. 27 deg.c) 

 and also dispersed yolky, round bodies (fig. 27 y). The characteristical 

 similarity of the cysts with the normal gono- or cytocysts of the 

 ontogeny of the germ-cells and also their presence near the gono- 

 or cytocysts (fig. 27) in the cranial part of the testes, prove beyond 

 all doubt, that we have here to do with cysts , which are prevented 

 from development and are going to degenerate, whilst the yolky Cle- 

 ments are derived from the cells, which form the contents of the cysts 

 (spermatogones or spermatocytes), Clear mitotical nucleus- 

 divisions were to be seen in the cysts, 



Both Investments of the testes continue on the vasa deferentia, 

 but they change in their structure. The pigmentation of the tunica 

 externa (fig. 28 ex) stops after having continued a short distance on 

 the vasa deferentia. The tunica interna too, has undergone 

 a change and seems to be a gland-epithelium (fig. 28 in). In their 

 commencement, the vasa deferentia {üg. 26 vd) rim caudally, bend 

 to the median and then they open into the ductus ejaculatorius 

 (fig. 26d.ej). They end in this ductus ejaculatorius on a common 

 papilla, each, however, with its own orifice. 



The ductus ejaculatorius is situated for the greater part in 

 the left half of the abdomen and runs caudally without winding. Here 

 it bends to the median, narrows and runs dorsally over the gut in a 

 cranial direction and opens into the sacculus ejaculatorius (fig. 26 

 sac). The part of the ductus ejaculatorius situated in the left half 

 of the abdomen, is lined by a gland-epithelium (fig. 29 in), of which 

 the cells are separated by very distinct intercellular fissures. Just as 

 we have seen in Leptis, where accessorial glands are missing, here 

 too, the function of these glands is taken over by other organs, partly 

 by the vas deferens and partly by the ductus ejaculatorius. 



The sacculus ejaculatorius (fig. 26 sac) is provided with an 



