532 • !*• E. Keuchenius, 



these cases the gland-liquid was already secreted during the larva- 

 sta<^e, and the secreta produced are evidently sufficient for the whole 

 imaginal life of the insect. I have not been able to find "Regenera- 

 tionszellen" (Escherich 7, p. 633). 



In several Diptera, the vasa deferentia and accessorial 

 glands if these are present, come out on a common papilla in the 

 ductus ej aculatorius, but in others [Eristalis, Rhingia, Dicranomyia) 

 on a papilla in the vesicula seminalis, and in this case, the ductus 

 ejaculatorius is the immediate continuation of the vesicula se- 

 minalis. 



The ductus ejaculatorius may have, as I have stated before, 

 a secreting function. In Lucilia and Tipula, the commencement of 

 the ductus ejaculatorius is bladder-like swollen, and this part 

 serves as a gland. [In other Diptera, too, such a bladdery widening 

 has been found at the beginning of the ductus ejaculatorius c. g. 

 by DuFOUR in Stachynia, Echinomyia, Sarcophaga (6, fig. 89, 97, 108), 

 and other specimens and by Swammerdam in Tabanus.] The ductus 

 ejaculatorius opens into the sacculus ejaculatorius and near 

 its end it is often invested by a layer of muscle-fibres. 



The vesicula seminalis is only to be found in a few Diptera 

 and seejns especially to be a characteristic of several Syrphidae. 

 It is a sack, which is blind at its cranial apex. It sometimes appears 

 to be a temporary depository for the sperm, {Eristalis) but in other 

 cases it has a secreting function [Rhingia, Dicranomyia). 



The sacculus ejaculatorius is lined by a chitinous intima in 

 all Diptera examined and it finds a way out through the, likewise 

 chitinous, ductus copulatorius. Only in the Tipulidae: Dicra- 

 nomyia was no apothetes ejaculatorius found by me. 



It is striking, that nowhere, around the testes or vasa defe- 

 rentia or accessorial tubes, or at the beginning of the ductus 

 ejaculatorius are there muscle-fibres to be found. We may conclude 

 from these facts, that the contraction of the abdomen, caused by the 

 abdominal muscles, together with the muscles of the sacculus eja- 

 culatorius, play a part in propelling the sperm and the fluids which 

 accompany it. 



Zool. Lab. Utrecht, in December 1912. 



