504 RICHARD EVANS. 



which for the greater part of their course are embedded in 

 the wall of the sac (fig. 51). 



The wall of the receptacidnm seminis is thin^ and consists 

 of two layers of cells. The outer layer is made up of flattened 

 cells belonging to the peritoneal epithelium; the inner layer 

 consists of short cells, with rather large nuclei and clear 

 cytoplasm. They contrast in the most marked way with the 

 columnar lining of the adjacent genital ducts (fig. 51). 

 The two narrow ducts of the receptaculum seminis lie for the 

 most part in its walls, and are lined with short columnar cells 

 provided with small and closely set nuclei. The receptaculum 

 seminis seems to be a storehouse, in which the spermatozoa 

 are kept until they are wanted. In Eoperipatus copulation 

 appears to take place, and the spermatozoa must pass up the 

 uterine canal into the receptaculum seminis. In one speci- 

 men which was sectionised the lower parts of the uteri were 

 absolutely full of sperm-cells, enough, it would seem, for a 

 lifetime. Indeed, it is difficult to understand how fecunda- 

 tion can take place in Eoperipatus once the ova have 

 entered the genital ducts, and have started on their journey 

 doAvn the uteri. Embryos in all stages of development are 

 found in the uteri, and probably go on developing all the 

 year round, so that the uteri are never empty. The natural 

 conclusion come to is that fecundation takes place only 

 once ; that is, before the ova have ever entered the uteri. 

 The receptacula seminis should be considered as a couple 

 of sacs formed for the purpose of retaining the sperma- 

 tozoa, w^iich are transmitted into the female uteri during- 

 copulation, which takes place before any ova have ever passed 

 down the oviducts to the uteri. 



The Receptaculum Ovorum : — In Eoperipatus there 

 are two receptacula ovorum with thick walls, exactly like 

 those figured and described by Gaifron as open funnels 

 (7), and by von Kennel as closed sacs (9), They occur only 

 in the genera Peripatus and Eoperipatus. Paraperi- 

 patus, Mesoperipatus, Opisthopatus, Peripatopsis, 

 9,nd Peripatoides have no receptacula ovorum. In Eo- 



