434 MONOGRAPH OF THE TEH NOCEPBALEjE : SUPPLEMENT, 



about the region between the antei'ior and posterior testes, and 

 their ducts form a strand running exactly in the position which 

 in his fig. 18 Monticelli assigns to the posterior vas deferens.* 

 The appearance which he figures is, in fact, presented by several 

 of my preparations of entire specimens of Australian species; 

 and it is only with difficulty that it can be clearly demonstrated 

 in these that the true interpretation is as I have stated. 



Monticellif states (t.c. p. 87) that the sac which is by Weber and 

 other authors termed receptaculum seminis and which I have 

 called receptaculum vitelli, is in T. brevicomis always filled not 

 with yolk but with spermatozoa. In the Australian and New 

 Zealand species, on the other hand, when any sperms at all are 

 to be detected in the interior of the receptacle, they are always 

 present only in small number, the bulk of the contents or, more 

 usually, the entire contents, consisting of the finely gi'anular 

 vitelline matter. This sac, in fact, acts as the receptacle in which 

 the vitelline matter collects in anticipation of the discharge of a 

 mature ovum from the ovary; when this discharge takes place the 

 vitelline matter is found to have become transferred to the uterus 

 in which the completed egg becomes formed — the receptaculum 

 being now empty or nearly so. It is the anterior part of the 

 oviduct that performs the function of retaining the sperms. The 

 proper designation of the receptacle is thus, in the Australasian 

 species at least, not receptaculum seminis, but receptaculum 

 vitelli. t 



* Compare this with fig. 1 of Plate xv. in my " Monograph." 



t Monticelli has misunderstood my statement with regard to the termina- 

 tion of these ducts. He says, " L'Haswell ('6, p. 13) non ha potuto seguire 

 l'ultimo decorso dei vitellodotte, ne accettarsi del punto di sbocco del con- 

 dotto vitellino." In the passage to which he refers I state distinctly that 

 that they open into the oviduct close to the ovary and receptaculum vitelli. 



J A precisely similar vitelline receptacle with similar relations occurs in 

 some Khabdocoeles. 



