12 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 



The receptaculum seminis of Peripatus, besides presenting the peculiarity of a double 

 duct, is very remarkable on account of its occurrence in the immediate neighbourhood 

 of the ovary, far removed from the vagina. It occurs in all the subgenera with the 

 exception of the Cape form; and it is always paired. In the young female, 17 mm. 

 long, to which Fig. 17 relates, the receptacula seminis were quite empty. In older 

 specimens, whether there are few or many embryos in the uteri, there is an abundant 

 supply of spermatozoa in the receptacula seminis; and, as they probably arrive there 

 by way of the vagina, it seems extremely likely that fecundation takes place once only, 

 in other words, that when a female reaches maturity, fecundation takes place, the 

 receptacula seminis are filled with spermatozoa and then ovulation begins. After 

 the embryos have begun to pass into the uterus no more fecundation can take place. 

 In the Cape Peripatus, the conditions are widely different. In the absence of receptacula 

 seminis, the spermatozoa penetrate into the ovary itself and fill up its cavity (Moseley 

 14). Moreover they appear rarely if ever to travel to the ovary by way of the vagina, 

 but they reach the ovary from the outside, being probably injected into the body- 

 cavity through the body-wall by the process described by Whitman as hypodermic 

 injection. In the case of leeches and other forms, this has been satisfactorily observed 

 (Whitman 24). In P. capensis Sedgwick (18) found that the small spermatophores 

 characteristic for this species were deposited upon any part of the body of the female. 

 This observation, combined with Moseley's description, confirmed by Sedgwick and 

 Sheldon, of the ovary filled with spermatozoa some of which projected through the 

 wall of the ovary into the body-cavity, is enough to justify Whitman's suggestion 

 that hypodermic injection of spermatozoa takes place in Peripatus as well as in 

 leeches. 



Receptaculum ovorum. In the Neotropical Peripatus there is a thin-walled diverti- 

 culum from each oviduct between the ovary and the receptaculum seminis. This sac 

 was mentioned and figured by Grube (7), but its true physiological nature was first 

 ascertained by Kennel (11). This structure only occurs in one known subgenus, 

 Peripatus s. str. 



Sedgwick suggested that it was morphologically equivalent to his nephridial end- 

 sac. In this case therefore the lumen of the ovary is merely a continuation of the 

 lumen of the oviduct, and the ovary and its duct are not two structures but one 

 structure. And this deduction is confirmed by the anatomical facts. The funnel of 

 the nephridium would thus be represented by the pore leading from the oviduct into 

 the receptaculum ovorum. This is also borne out by the histology of the parts in 

 question (Kennel 11, Pt. II) and, as is known, the receptaculum ovorum was described 

 by Gaffron (6) as the " Ovarialtrichter." In P. novae-britanniae, as we have already 

 indicated, the appearances are in favour of a distinction being drawn between ovarial 

 tube and oviduct. 



The presence and absence of receptacula ovorum seem to be correlated with the 

 occurrence of what I have called "epithelial ova" and "follicular ova" respectively. 

 In the latter case the stalks of the follicles represent so many secondary ducts dis- 

 charging into the main ovarial cavity. The latter therefore functions as receptaculum 

 ovorum. 



