3t38 PLA.TTHELMINTHES. 



straight median canal on the ventral surface, and opens by a short, narrow tube 

 into the oviduct. The vagina also functions as a receptaculuin seminis. There 

 is yet a third opening (fig. 275, a), situated at some distance behind the other 

 two ; this is the opening of the tubular uterus (Z7), the convolutions of which 

 give rise to a peculiar rosette-shaped figure in the midst of the segment 

 (Wappenlilie Pallas). Close to the hind end of the segment the ducts of the 

 yolk-glands (JDsf) and of the ovaries ( Ov) unite with each other and open into 

 the uterus ; the cells of the shell-gland (fid) surround and open into the point 

 of junction of these structures. Behind the uterus, and partly among its 

 posterior lateral horns, lie the so-called coiled glands ; and at its sides are 

 the so-called lateral glands (Eschricht). The latter are, according to Eschricht, 

 the ovaries or germaria (formerly held by Leuckart to be the vitellaria). 

 The coiled glands (Leuckart's ovaries), an aggregation of pear-shaped cells, 

 were considered by Stieda, with whom Landois and Sommer are in accord, to 

 be a shell gland (fig. 275). 



The ova are for the most part developed in water, and escape from the upper 

 pole of the egg-shell through a lid-like valve. The escaped embryo is covered 

 with cilia, by means of which it swims about for a long time. Hence it is 

 probable that the later stages of development take place in an aquatic animal. 

 It is unknown how and in what host the embryo with six hooks becomes a 

 Scolex ; and the question how this tape-worm gets into the human body in 

 spite of the researches of Knoch, who maintained that they appeared there 

 directly and without the intervention of an intermediate host is still un- 

 decided. B. cordatus Lkt. With large, heart-shaped head, without a filiform 

 neck ; with numerous deposits of calcareous bodies in the parenchyma. It 

 attains a length of about three feet and lives in the intestines of man and of the 

 dog in Greenland. 



Schistocephalm Crepl. Head split, with a sucker on each side. The body 

 of the cestoid form is segmented. S. solidus Crepl. Lives in the body cavity 

 of the stickleback, escapes into the water, and becomes sexually adult in the 

 intestine of water-birds. TricenopTiorus Hud. Head not distinct, with two 

 weak suckers and with two pairs of tridentate t hooks. The body has no external 

 segmentation. The generative openings are marginal. T. nodulosus Kud, In 

 the intestine of the pike. Asexual encysted form in the liver of Cyprinus. 



Fam. Ligulidae (Pseudopliyllid(B). Without real suckers. Hooks are either 

 present or absent. The Cestoid has no segmentation, but the generative organs 

 are repeated. They live in the body cavity of Teleosteans and in the intestine 

 of birds. Ligula Bloch. Body band-shaped and unsegmented. L. simpli- 

 cissimu Kud., in the body cavity of fishes and in the intestine of aquatic birds, 

 L. tuba v. Sieb., in the intestine of the Tench. 



The families of the Tetrarhynchidae (TetrarliyncTius lingualis, Guv., passes 

 its young stages in Soles, and is matured in the intestine of Eays and Dog-fish), 

 and Tetraphyllidae (EcMncibothrium minimum van Ben.) are allied here. 



Fam. Caryophyllaeidae. Body elongated and unsegmented. The anterior 

 margin is plicated. There are no hooks, and there are eight sinuous longitu- 

 dinal canals of the excretory system. Generative organs single. The develop- 

 ment is a simplified metamorphosis. Caryopliyllteus mutabilis Hud., in the 

 intestine of Cyprinoids. The young form possibly lives in TuHfex rivulorwu t 

 if the Helminth observed by d'Udekem was the same. In this worm^ however, 

 there lives another parasite, which was observed by Eatzel and has recently 

 been more closely investigated by R. Leuckart, who has shown that it is 



