Mvlhinh-infestiug Trematodes. 103 



gonad usually is, but tluit or;^an is quite obliterated. The 

 liver is move or less infected, in (he Holy Island specimou 

 lianlly at all. Each sporocyst is about O'lj mm. long and 

 0'15 mm. broad. It is colourless, transparent, and some are 

 very contractile, astuiming ail kinds of sliapes, while others 

 are itieit and move litile. Inside the sporojysts are small 

 granules and large opaque round masses from two to twelve 

 in number, which, ou closer examination, are seen to be 

 encysted cercarii?. More or loss develoj)ed tailed cercariae 

 are also sometimes to be seen in the sporocysts along with 

 the encysted forms. They are very contractile and are con- 

 stantly shifting their jx>sition inside the sporocyst, the tail 

 moving incessantly. Tiie ceicaria sheds its tail before 

 encysting, and in several sporocysts tails were to be seen 

 moving quickly round the encysted worms when only these 

 latter were present in the s|)orocysts. The free tails were 

 excessively active. The cyst is about O'li mm. across and 

 is very thin. The enclosed cercaria is seen to be covered 

 with short spines and has two suckers, both usually visible 

 when the worm is curled up in the cyst. When pressed out 

 from the cyst it is about 0"iy mm. long (see PI. VII. B), the 

 spines covering it are conspicuous and form circuUir rows 

 round the anterior sucker and all over the body. The ante- 

 rior sucker is large (O'Ot mm. across), and leads by a short 

 oesophagus to a tliick-lipjied ])harynx (which, however, often 

 appears to be continuous with the sucker owing to the con- 

 tracting of the animal). The pharynx leads to the intestine, 

 which almost immediately bifurcates into two lobes, reaching 

 nearly to the posterior end. The small ventral sucker is 

 fclightly posterior to the centre of the body. There is a large 

 clear excretory sac opening posteriorly, but excretory canals 

 could not be distinctly made out. Tlie tailed cercaria (see 

 PI. VII. C) is much the same, but thes[)ine3 had not appeared 

 in those I saw and the intestine did not branch so soon, 

 probably because the worm was stretching itself more than 

 the encysted form. Two ducts each side of the anterior 

 sucker can be indistinctly seen, probably coming from the 

 glands which serve for tiie secretion of the material for the 

 cyst, as they disappear in the later stages, after the worm 

 has encysted. Tlie intestine is very indistinct, owing to the 

 opacity of the animal, and can only be completely seen by 

 stiiining. 



'Ihe less-developed cercariaj in the sporocysts arc small, 

 granular, oval masses, then a trace of a tail a])pears, after 

 that the clear excretory sac is seen, then the anterior sucker, 

 and later the posterior sucker. The cercaria may be half the 



