SANGUINICOLA 239 



cells which had become prematurely or accidentally shed into 

 the ' uterus '. 



Concerning the existence of vitellaria as distinct from ovarian 

 follicles, I am unable to speak with certainty from actual 

 observation, since, as Dr. Plehn admits, they are not in any way 

 distinguishable, and I am willing to allow that, if vitellaria exist, 

 the upper part of the oviduct may function as a vitelline duct, 

 but as regards the existence of a separate female duct, i.e. 

 combined ' Dottergang' and ' Uterus' (PI. 18, fig. 11) in addition 

 to the oviduct figured by Dr. Plehn in her original communica- 

 tion (and by me in fig. 1) and relabelled ' vagina ' in her second 

 paper, I am absolutely certain that, in the Sudan Sanguinicola, 

 such a second female duct does not exist (as I can demonstrate 

 in both whole-mounted specimens and in horizontal and trans- 

 verse sections) and, since there is no shell-gland and Dr. Plehn 

 did not observe this second female duct when first describing 

 the genitalia, 1 feel tolerably certain also that it does not exist 

 in the German Sanguinicola.^ Further, the non-existence of 

 a separate vitelline duct almost imphes the non-existence of 

 vitellaria, as also does the presence of globules of presumably 

 some sort of food material in the periplasm of the eggs (PL 18, 

 fig. 10). As regards the existence of an ootype, a true ootype, 

 i. e. a chamber into which the ducts of the vitellaria and shell- 

 gland open, obviously cannot exist, since both vitellaria and 

 a shell-gland are absent ; but if it did, it would presumably be 

 found next to the fertihzation chamber which I have described 

 and not between the ovaries. Finally, I can see no reason to 

 suppose that the eggs found inside the fertilization chamber 

 are not mature : their position alone certifies their maturity. 



In short, the female reproductive system of Sanguinicola is 

 in essentials constructed upon the plan found in many Ehabdo- 

 coelida and Polycladida, in which vitellaria are also absent and 

 in which the oviduct is also long and opens directly to the 

 exterior, its end part being differentiated into a fertilization 



^ If this second female duct does exist in the German Sanguinicola, then 

 this is radically different from the Sudan form, but this I am unable 

 to credit without further evidence. 



