516 P- E. Keuchenius, 



ejaculatory apothetes (fig. 26«/)), which is connected by volun- 

 tarv-miiscle-fibres witli the wall of the sacculus. The sacculus 

 opens to the outside by means of the ductus copulatorius (fig. 26 

 d.cop). In their structure the sacculus and ductus copulatorius 

 resemble to the specimens described above. 



Lucilia caesar Linn. (Fig. 30 — 36). 



In fig, 30 there is to be seen a diagram of the structure of the 

 male internal genital apparatus of Lucilia caesar. They are composed 

 of one pair of testes, vasa deferentia, accessorial gland-tubes, 

 ductus ejaculatorius and sacculus ejaculatorius. 



The testes (fig. 30 f) are two more or less oblong bodies and 

 sometimes are entirely surrounded by fat-body-tissue, which in 

 this case is only at some places intimately connected with the testes. 

 The testes are situated ventro-laterally of the gut, the right more 

 cranially than the left. Again the tunica externa and interna 

 form the only investments. The tunica externa (fig. 31 ex) is a 

 lightbrown pigmented cell-layer of changeable thickness, in which 

 here and there are to be seen very large nuclei, surrounded by a clear 

 protoplasm (fig. 31 w). The tunica interna is a flat epithelium 

 being of a cellular nature only quite caudally, near the transition of 

 the testes into the vasa deferentia. I saw cellular septa going 

 out of the tunica interna and pushing into the lumen of the testes. 

 These septa may be ramified (fig. 31 sept). The interna loses its 

 cellular character in a proximal direction and continues in the mem- 

 brana propria. Proceeding from the proximal part to the distal 

 (fig. 31), one finds the testes filled up respectively with: gonocysts, 

 cytocysts, spermatocysts and bundles of ripe spermatozoa. 

 Hence the youngest stages of the ontogeny of the germ-cells were 

 not observed by me. In the cysts we may observe clear mitotical 

 nucleus-division-figures. Besides these elements there are to be found 

 m the testes globular groups of cellular bodies and I also saw such 

 cellular bodies dispersed. (fig. 31 deg.c and y). Here too, these ele- 

 ments gave me the impression of being degenerated cysts. 



Both coverings of the testes form also the only investments of 

 the vasa deferentia. The tunica externa (fig. 32 ex), however, 

 loses, after a short distance, its pigmentation onthe vas deferens, 

 wHle its nuclei are much smaller than on the testes. In the tunica 

 interna (fig. 32 m) the nuclei are round and very close to each other. 



The accessorial glands (fig. 30 acc) are rather wide tubes, 



