REPTILIAN TAPEWORMS. 19 



dorsal and a ventral, fairly evenly suijerposed. The calibre of 

 these vessels is not large, and they do not dilfer greatly in size. 

 I have observed branches going towards the extei'ior, but have 

 not ti-aced them as far as an opening. The longitudinal trunks- 

 lie sometimes to the inside of, and sometimes above and below, the 

 vitelline mass. 



The testes, as can be best seen in transverse sections, form a 

 layer, only one deep, of 80-100, or even more, in a single pro- 

 glottid. While there is not a median space entirely free from 

 testes in this species such as occurs in some other species of the 

 genus, the testes are often not quite so densely arranged in the 

 median area ; they occur there, however, even when the uterus 

 is fully formed, in the thickness of the strands which form its. 

 diverticula. The testes do not extend back to the sides of the 

 ovary, but anterioidy they may (or may not) reach quite to the. 

 end of the segment. 



The vas deferens, after issuing from the cirrus-sac, forms a> 

 dense coil, which extends over about half of the breadth of the 

 proglottis. It lies at right angles to the long axis of the pro- 

 glottis, and is directed neither forw^ards nor backwards. The 

 tube forming this coil is thin- walled and of wdde calibre. Within 

 the cirrus-sac the sperm-duct is also coiled, but it is here of much 

 less calibre. I was not able to see any hooks in connection with 

 the copulatory apjoaratus. The aperture of the cirrus-sac was 

 always in front of the orifice of the vagina. The cirrus-sac is 

 flask-shaped as in other Ichthyotjeniids and in many tapeworms^ 

 but there is not so shai-p a demarcation between the two reo-ions; 

 as is so commonly the case. The walls are thin and obviousl3r 

 muscular ; they are not thicker in the neck of the cirrus. It. 

 is necessary to insist upon the muscularity of the walls of the 

 cirrus-sac since Schwarz * has written of that of Ichthyotcenia 

 nattereri: "Die Blase (i. e. of the cirrus-sac) ist diinn, nicht. 

 muskulos." It should be mentioned that the alternating gene- 

 rative pores lie some way behind the middle of each proglottid f. 



The ovary is, as usual, in two portions, with a slender bridge im 

 the middle line uniting the two. The contour of the ovary^ 

 though irregular, is not pulled out into digitiform ]3rocesses as in 

 Ichthyotcenia hiroi. The vagina runs parallel with the cirrus-sac 

 and posterior to it, as already mentioned. This region of the tube 

 is wider than that lying behind ; but the vagina is here not 

 coiled, and, indeed, scarcely wavy in O'utline. Posteriorly between 

 the wings of the ovary the vagina is coiled for a short distance.. 



* Log. cit. p. 20. 



t In one proglottid, wliicli was iwWj ripe and contained numerous embryos, I 

 observed a remarkable variation wbicli I have not seen before in a tapeworm. The- 

 cirrus-sac with the succeeding- large and comple.v coil of the vas deferens was particu- 

 larly obvious ; but the most careful examination failed to show a vagina lyino- either 

 in front of or behind the cirrus-sac. But by following up the vagina from the ovary 

 forwards it was found to bend in the reverse direction and to open on to the opposite 

 side of the proglottid, nearly on a level with, but slightly behind, the line of openino- 

 of the male pore. I regard this state of affairs as merel}' a variation, but I have not 

 read of anj- parallel instance. 



2* 



