SOME MAMMALIAN TAPEWORMS. 655 



posterior end of the sucker its tissues come to an abrupt end, and 

 I invariably found a shallow cavity between the sucker and the 

 medullary tissue of the head. This suggests that the original 

 position of the sucker is more apical and that it is directed 

 upwards — a state of aflairs which is actually seen to persist in 

 many species of Tetracotylea. 



The orifices of the generative organs are, as already stated, 

 completely unilateral. I have examined pieces of the worm 

 mounted whole, and many series of sections, and find that in 

 every case there is a regular sequence of the apei'tures which lie 

 upon one side of the body *. These orifices are not conspicuous 

 on examination with a lens, as they are in many Tapeworms, and 

 for two reasons. In the first place, the orifices are actually small, 

 and in the second place, I have never observed the cirrus to protrude. 

 Thus it is necessary to make a microscopical examination in order 

 to detect the genital pores. Apart from microscopic sections, 

 where, of course, it is easy to find the pores, I have only observed 

 them (that is, in pieces of the worm mounted entire) in the wider 

 posterior segments. Here they are seen to lie at just about the 

 middle of the proglottides. The orifices project slightly and are 

 quite circular. 



The excretory system of this Tapeworm presents certain unusual 

 features. In transverse sections through some of the middle 

 segments of the body there are four longitudinal canals perfectly 

 obvious in the body and no more than four, unlike, for instance, 

 the genus Oochoristica, with which the present genus has some 

 characters in common. These four tubes are lateral in position, 

 and are all of them at about the same level. It is thus impossible 

 by position to distinguish the dorsal from the ventral excretory 

 canals. The two on each side are at a considerable distance apart. 

 The distance which separates the outer from the inner of the two 

 is about as great as that which separates the outer tube from the 

 nearest margin of the body. The tubes can, however, be dif- 

 ferentiated by their size. The outermost of the two excretory 

 canals is not more than one-third of the diameter of the inner- 

 most tube. The form is not, however, so small that it can be 

 missed in transverse sections. In the very anterior segments I 

 have noticed a third lateral vessel on each side ; and in this region 

 of the body, moreover, the two main tubes have a greater incli- 

 nation respectively to the dorsal or ventral side. There is an 

 abundant plexus of vessels connected with these and traversing 

 the proglottides, but I am unable to give details. I think, 

 however, that I have seen numerous external pores. 



The testes have a somewhat peculiar arrangement, which is 

 distinctive of this worm. The bulk of these very numerous 

 gonads lie upon that side of the body upon which the generative 



* I cannot determine whether this is right or left with certainty, since in trans- 

 verse sections the gonads are not definitely dorsal or ventral in position, i. e. nearer 

 to one surface of the proglottid or the other, while the dorsal and ventral excretory 

 tuhes are parallel to each other and lie in the same plane with the nerve-cord. 



46* 



