The structure of the internal Genitalia of some male Diptera. 517 



which for tlie greater part have their Situation in tlie left side of the 

 abdomen. They begin caudally and run in cranial direction without 

 \vinding and just near their end, they turn to the median, at the sarae 

 time narrowing a little. Dufour gave us a drawing of the genitaha 

 of Lucilia caesar, in which both accessorial glands are drawn laterally 

 on each side of the ductus ejaculatorius (6, pl. IX, fig. 113). This, 

 however, is incorrect, because both are situated on the left side of 

 the ductus ejaculatorius. Hence it is obvious that, without maldng 

 microtoniic sections, one is extremely liable to make mistakes, regard- 

 ing the position of the internal genitalapparatus. 



The tunica externa of the accessorial gland-tubes (fig. 33 ex) 

 is thin and provided with small nuclei. The interna isa giand-epithe- 

 lium of which the cells are provided with round nuclei. The proto- 

 plasm of the epithelium gets less intensively coloured at the base of 

 the cells than at the side turned to the lumen of the gland-tubes 

 (fig. 33). The lumen is filled up with weakly colouring secreta. 



The accessorial gland-tubes and vasa deferentia open 

 on a common papilla in the ductus ejaculatorius (fig. 34:pap) but 

 all tubes have their own orifices. A very peculiar formation is to be 

 found at the commencement of the ductus ejaculatorius. This 

 is swollen at the outside in the form of a bladder, a thing which was 

 already observed by Dufour (fig. 30). Microscopical research proves, 

 however, that there is no question about a real formation of a bladder, 

 because the lumen (fig. 34 lum) is not a bit larger than elsewhere in 

 the ductus ejaculatorius. The epithelium-cells, however, are very 

 high here, whilst in the protoplasm there is to be seen a very strong 

 vacuolisation. The nuclei of these gland-cells are situated at their 

 base and the protoplasm here gets more strongly coloured than the 

 vacuoles. We have consequently to do with a gland. However, it 

 is stränge, that in some specimens this gland should not have been 

 found by me. I suppose, that in this case these specimens were younger 

 adults. Gradually at the end of this swollen part of the ductus eja- 

 culatorius, the epithelium-cells receive their normal non-secreting 

 character. The externa of the ductus ejaculatorius consists of a 

 very thin cell-layer with flat nuclei (fig. 34 ex). The ductus eja- 

 culatorius runs caudally and opens into the sacculus ejacula- 

 torius (fig. 30 d.ej and sac). Distally we see that the tunica externa 

 of the ductus is composed of more cell-layers, while at the same time 

 a very fragile transversal striping is to be noticed (fig. 35 m). Evident- 

 ly the outer wall of the ductus consists of voluntary muscle-f ihres. 



Zeitschrift f. wissensch. Zoologie. CV. Bd. 34 



