52i P- E. Keuchenius, 



reiitia, accessorial glands^ ductus ejaculatorius and sacculus 

 ejaculatorius, in other words the same organs we bave already 

 met with in several Diptera. We shall, liowever, see in what follows, 

 that some organs are more or less divergent. 



The testes (fig. 55^) are two oblong bodies, wbicb bave tbeir 

 Situation ventro-laterally of tbe gut. Tbeir longitudinal axes run about 

 parallel to tbe median line. Tbe rigbt testis is tbereby placed a 

 little more cranially tban tbe left. Botb testes are quite enclosed 

 by fat-body-tissue, wbicb is very intimately connected witb tbe 

 outer investments of tbe testes. Tbe finer structure of tbe testes 

 of Tipula was already examined by Cholodkovsky (3, p. 401). How- 

 ever, be does not speak anywbere of tbe fat-body-tissue, wbicb 

 exactly bere surrounds tbe testes very strikingly. According to 

 Cholodkovsky tbe testes are invested by two layers. Tbe tunica 

 externa is a tbin layer witb nuclei and wbicb tears off very easily, 

 wbilst tbe inner investment is formed by a layer of epitbelium. I bave 

 not been able to find any trace of an outer investment (tunica externa) 

 in my numerous sections of Tipula oleraceo, but possibly it consists 

 of an exceedingly delicate membrane witbout nuclei. Tbe interna 

 (if I may speak about a tunica interna, because tbere is only one 

 investment) consists of a flat epitbelium, wbicb bowever, is variable 

 in tbickness and is to be observed on tbe wbole surface of tbe testes, 

 so tbat no membrana propria is formed (fig. 56, A). Against tbe 

 outer-surface of tbe epitbelium, many tracbeal trunks are ramified. 

 As Cholodkovsky bas already observed, (3, p. 402) in tbe epitbelium 

 tbere are to be found vacuoles, wbicb are filled up witb larger or 

 smaller granules and wbicb got coloured very intensively in my sec- 

 tions (fig, 56, B and C, vac and y). Tbese vacuoles are expelled by 

 tbe epitbeHum and tben tbe granules arive in tbe lumen of tbe testes 

 (fig. 56, A, y). Probably tbey play a part in tbe nutrition of tbe different 

 stages in tbe ontogeny of tbe germ-cells. Tbe testes are filled 

 witb bundles of ripe spermatozoa, between wbicb, besides tbe above 

 mentioned granules tbere are otber, less strongly colouring, dispersed 

 globular bodies (fig. 56, A, x) to be found. Tbese globular bodies 

 remind me of tbose I bave met witb in Rhingia rostrata and Syrphus 

 ribesi. Probably tbe investigation of tbe ontogeny of tbe spermato- 

 zoa may discover tbe origin of tbese elements. 



Tbe epitbelium of tbe testes continue on tbe vas deferens 

 and bere, too, it forms tbe only investment. It is, bowever, more 

 regulär and not provided witb granules-containing vacuoles. Tbe 



