SOME MAMMALIAN TAPEWORMS. 635 



the body, wherein the genital ducts had not attained their full 

 development. In siich a segment the testes are seen to be 

 distinctly more numerous than in such segments as have just 

 been described, a transverse section would show fully twenty 

 testes in a given plane (in the I'egion of the proglottid where 

 they ai^e most abundant). At the same time, these gonads 

 are much smaller. I have sections of proglottides which show an 

 intermediate state of affairs, and in which the posterior testes are 

 large and appar-ently full-grown, while anteidoily the testes ai-e 

 very small and quite similar to those of immatui'e or only in- 

 completely mature segments. These immature testes had no 

 membrane that I could detect. It appears to me that the advance 

 in growth of these gonads is achieved by the inclusion within a 

 common membrane of areas of testicular growth which have 

 separately originated and which in the very youngest stages can 

 be seen to consist of a single cell only. It will be observed that 

 the disposition of the testes of this species is quite like that of 

 some other forms belonging to this genus as described by 

 Janicki *. 



Several fortunate sections have enabled me to see very clearly 

 the ari'angement of the vas deferens and its mode of tei"mination. 

 This tube is loosely coiled not far from its entry into the cirrus 

 sac. Befoi'e it enters the latter it passes in a straight course and 

 enters at the very extremity of the sac. It is noteworthy that 

 this duct is quite double the width of the vagina at its opening 

 into the genital cloaca and for some distance behind this point. 

 The vas deferens when it enters the cirrus sac at once swells out 

 into a small vesicvila seminalis, which thus lies within the ciri'vxs 

 sac instead of outside as in most cases. The vesicula does not 

 by any means fill even the end of the cirrus sac in which it lies. 

 Immediately after this the duct narrows again, and again imme- 

 diately swells out into a smaller dilatation. After this comes the 

 narrow cirrus itself. The walls of the cirrus sac are loose and 

 muscular. 



Liihe, the founder of this genus, in some notes t upon the 

 anatomy of species of Oochoristica from Lizai-ds (for example, 

 TcBnia Uiherculaia of Rudolphi), remarks that the development of 

 the uterus must be extraoidinarily rapid, as so often no intei'- 

 mediate stages are obvious between a fully developed ovary and 

 the scattering of the mature eggs in the pai-enchyma. I quite 

 agree with Liihe, for the reason that the uterus is not always to 

 be found and is at least by no means so characteristic of this 

 particular Tapeworm as it is of many others. There are, how- 

 ever, stages to be observed. I have never seen more than a small 

 elongated sac lying near to either the ventral or the dorsal side of 

 the segment. In longitudinal sections this sac shows a tubular 

 form, and is, indeed, so narrow a tube that on first observing it I 

 mistook it for one of the excretory vessels, and imagined that the 



* Zeitschi-. f. wiss. Zool. Ixxxi. 1906. 



t " Oochoristica iiov, gen. Tseniadarum." Zool. Aiiz. xxi. 1898, p. 65U. 



