80 Records of the Indian Museum. [Vol. XV, 



given off, anteriorly, a very small oviduct (O.d). The two oviducts 

 unite in the middle-line and receive, at the point of junction, the duct 

 of the shell-gland (S. G). This organ lies between the ovaries, in 

 the centre line. The uterus (Ut) originates, anteriorly, from the 

 point of union of the two oviducts. It runs forward in the middle-line 

 as a blind diverticulum, practically to the anterior termination of the 

 proglottid, narrowing as it goes. The vagina (V) also originates 

 close to the mouth of the uterus and is continued as a narrow coiled 

 tube to near its opening. It then widens to form a barrel-shaped 

 receptaculum seminalis (R.S). 



Water-vascular system (plate iv, fig. 3). — This consists of a single 

 pair of wide tubes (W. T), situated one on each side, internal to the 

 excretory vessel and nerve. These two tubes communicate with each 

 other by a wide transverse vessel situated at the posterior margin of 

 each segment. In the head, the two tubes break up into a series of fine 

 vessels distributed throughout the substance of the head. 



Excretory system (plate iv, fig. 3). — This consists of a pair of very 

 fine tubes (E. D) situated, one on each side, between the water- 

 vascular vessel and the nerve. In the proglottides, they do not unite, 

 but in the head they are united by a single transverse vessel. 



Nervous system (plate iv, fig. 3). — In each proglottid this consists of 

 a single fine nerve (N) on each side, external to the water-vascular 

 and excretory duct. No attempt was made to follow the distribution 

 of the nervous system in the head. 



The larva. — We have already referred to the fact that numbers of 

 tadpole-like cysts were found in the lateral muscles of the partly digested 

 Hilsa, Previous to this record no cysts had been noticed in the flesh of 

 Hilsa, although some time ago larval forms of Syndesmohothrium fiUcolle, 

 Linton, were recorded by one of us from the mesenteries of this fish 

 (5 & 6). The Rhynchohothrius cysts were, as noted, tadpole-shaped 

 (plate iv, fig. 5). They consisted of a club-like head, and a long tail- 

 like structure which was capable of considerable movement, and ap- 

 peared to us to serve the purpose of mooring the larva in the intestine 

 of the shark, during the digestive processes. 



The head, in one specimen, measured 4-8 mm. by 3-6 mm. The tail 

 tapers to a point and measured 51-8 mm. in length. On opening out 

 the " head," the larva (Y) was seen to be a massive structure occupying 

 the greater part of the head and lying in a coiled position (plate iv, fig. 6). 

 The tips of the four proboscides were just everted, and the spines 

 could be clearly seen. Many young worms (plate iv, fig. 7) were also 

 obtained from the lumen of the intestine. These had not had time to 

 attach themselves to the intestine of the host. 



Life-history. — The Cestodes usually complete their life-histories in 

 two separate hosts, the larval form occurring in an animal which is 

 devoured wholly, or in part, by the final host of the worm. In a great 

 number of cases the larval forms of adult worms have not been re- 

 corded. In fewer instances larval forms have been described, but the 

 adult worm developing therefrom is not known. The circumstances 

 under which we are able to follow the life-history of this worm are un- 

 doubtedly unique. In the present instance, the larval form of Rhyn- 



