322 PLATTHELMIXTHES. 



Diatomiim. Median sucker approached to the anterior one. It. Ju-jwticum L, 

 Liver fluke. With conical anterior end. and numerous spine-like prominences 

 on the surface of the broad leaf-shaped body, which is about 30 mm. long. 

 Lives in the bile-t!u?ts of sheep and other domestic animals, and produces 

 the liver disease of the sheep. It is occasionally found in Man, and bores its 

 way into the portal vein and into the system of the vena cava. The elongated 

 embryo only develops after the egg has remained a long time in water : it has 

 a continuous ciliated envelope with an X-shaped eye-spot. E. Leuckart's re- 

 searches have rendered it probable that the development is passed through in 

 the young Limntzus ziererjcr and trimcatvlvs, that here the embryo becomes a 

 ,^/Hirocyst. and that this produces Hcdia, in which it is supposed that tailless 

 Digtomea arise. 



[The life-history of the liver-fluke has been completely worked out by A. P. 

 Thomas {Quart. Journal of Mica-oscopical Sci. 1883, pp. 99 133). He -has 

 shown that the ciliated embryo passes into Limnceits ti'uncatulus, ami there 

 gives rise to a sjinrocyst which produces redias. The ri-dia; produce more 

 redice or Cercariee. The Cercarlee, which are provided with long tails, leave 

 the host (Limncevs trimcatiilvs"), swim about for a short time in the water, and 

 encyst on foreign objects, e.g. blades of grass. In this condition they are eaten 

 by the sheep.] 



D. crassiim Busk., in the alimentary canal of the Chinese, one to two inches 

 in length, and half-inch broad, without spinous prominences, with a simple 

 forked intestine. D. lanccolatum Mehlis. Body elongated into the form of a 

 lancet, 8 9 m.m. long, lives in the same place with D. licpaticum. The embryo 

 develops at first in water, is pear-shaped, and only ciliated on the anterior half 

 of the body, bears a styliform spine on the projecting apex. D. oplithalinoibium 

 Dies. A doubtful species of which'only four specimens have been observed in the 

 lens capsule of a nine-months' child. D. JteteroyJtyes Bilh. v Sieb. 1 1-5 rnm. 

 long, in the alimentary canal of man in Egypt. D. goliath van Ben., 80 mm. 

 long, in Pteroljalaina. Numerous species live in the alimentary canal, lungs, 

 and bladder of the frog. Uistomttnjilicolle Rud. (Z. Olteni Kb'll) in pairs -in 

 the mucous sacs in the branchial cavity of Brama Raj I. The one individual is 

 cylindrical and narrow, and produces spermatozoa ; the other is swollen in the 

 middle and posterior region of the body, and is filled with eggs. The dissimilar 

 development of the two individuals is probably due to the fact that copulation 

 only leads to the fertilization of one of them, which alone is able to perform 

 the female sexual functions. D. licematobium. Bilh. v. Sieb. (GyncecfljtJtorus 

 Dies) (fig. 257). Body elongated ; sexes separate. The female is slender and 

 cylindrical. The male has powerful suckers, and the lateral margins of the 

 body are bent round BO as to form a groove, the canalis gynaacophorus, for the 

 reception of the female. They live in pairs in the portal vein, and in the veins 

 of the intestine and of the bladder of man in Abyssinia. According to Cobbold, 

 the embryos are ciliated, and possess a tolerably well developed excretory 

 system. By the deposition of masses of their eggs in the vessels of the mucous 

 membrane of the ureter, bladder, and great intestine, inflammation is set up, 

 which may cause hrcmaturia. 



(2) Sub-order: Polystomea. TYematocles with two small lateral 

 suckers at the anterior end, and one or more posterior suckers, to 

 which two large chitinous hooks are often added. In exceptional 



