83 s. GOTO. 



The above account of sperniatoo'enesis lias heen based on observa- 

 tions OÏ MlcrocotijJc caiidaia ; but the process is essentially the same in 

 all the genera treated of in this paper. It will be seen that it (lifters 

 in many res])ects from the statements of other writers'' on the same 

 subject ; but the various stages observed seem to me to be capable of 

 orderly arrangement only in the w;iv indicated nbove. The process of 

 spermntogenesis -dx^ve descril)ed nlso differs considerably from that 

 which t^kes ])l:ice in DipJozoou (IM. \\^ hg. 4). In this the sperm 

 mother-cell iirst divides by ordinary mitosis, then effects what has 

 been termed reduction-divisiori ; and each (hiu2:hter-cell thus formed 

 developes into a spermatozoon, in which the chromos(mies can still be 

 distinctly seen. Finally the mode of division above descril)ed is so 

 different from ordinnrv mitosis that I am not able to say what 

 relation it bears to that. This and (^ther ol)scure poiiits indicated 

 above I must leave to future investigatioris. 



A^AS DEFEr^EXS — Iri Tristoiniim the vasa etferentia that proceed 

 from the testes can in most cnses be traced out ; but this is possible 

 only when thev are made visible l)y being tilled with spermatozoa, 

 which stain very dee])ly with most colouring fluids. The vasa 

 etferentia unite with one another and finally foi'm a ]):u'r of large 

 vasa etferentia, which again unite with each other in the median 

 line of the body and form a single vas deferens. This is at first of 

 small calibre, but liecomes gnidually larger îind larger as it proceeds 

 forwards on the left side of the ovary, and after undergoing numerous 

 smaller windings, forms just in front «^f the ovary, a, large loop, the 

 closed end of which is directed towards the right side of the l)ody, and 

 in most species also more or less forwards (PI. XX, fig. 1 ; PI. XIII, 



1). Kerbert — Beitrag z.ur Kenutniss der Treinatoden. Archiv f. mik. Anatomie, Bd. XIX, 

 1881. p. 559 et infra. Also Monticelli — (According to Braun's report in Centralhlatt f. 

 Bakteriologie u. Parasitenknnde, XTTI. Bd., 1893, p. 180). 



