INTESTINAL WORMS. 175 



the Scolex can gain a passive migration into the intestinal canal of 

 an animal suitable for its development, that development will 

 proceed; the vesicle will be cast off: joints will be formed suc- 

 cessively beneath the neck, and in these joints the genital organs 

 will be developed, the joints first formed, or nearest the posterior 

 extremity of the body, being the first to become mature. Thus the 

 Scolex is changed into a Tape-worm. Many naturalists now con- 

 sider the Tasnia3 to be compound animals, (which indeed was the 

 opinion long ago of VALISNIERI and COULET and afterwards of 

 BLUMENBACH,) colonies, like certain Polyps: the head and neck 

 corresponding to the Polyp-stock, and the joints, under the name of 

 Proglottis, to the single Polyps. By such observations as these 

 VON SIEBOLD has been enabled to interpret justly those of LEBLOND 

 and MIESCHER alluded to above. The Amphistoma of LEBLOND 

 was the embryo of the Tape-worm, now the receptaculum Scolecis, 

 the TetrarhyncJius the Scolex of a RJiyncotothrius. When the 

 minuteness of these embryos is considered (they are not more in 

 volume than the blood-disc of the frog) it is not difficult, as VAN 

 BENEDEN * says, to comprehend that they may perforate the walls of 

 the intestine to encyst themselves beneath the peritoneum, or to 

 penetrate the vessels and distribute themselves with the blood in 

 different viscera of the body, not excepting the brain itself, or the 

 humours of the eye. Dr HAUBNER of Dresden caused six young 

 lambs to swallow the living and mature joints of Tcenia serrata. 

 They all died of the peculiar vertiginous disease produced by 

 Ccenurus cerebralis. The Ccenurus vesicles were found in the brain, 

 and the heart, lungs, and voluntary muscles abounded with encysted 

 broods of Tcenia 2 . It would seem from this that the different forms 

 of Ccenurus and Cysticercus assumed by the larva depend upon the 

 locality occupied by the embryos, and the quantity and nature of 

 the nutriment which they obtain there. And this conclusion is 

 confirmed by the previous and converse experiments of VON SIE- 

 BOLD. On causing young dogs to swallow Cystic, pisiformis from 

 the liver of the hare, Cist, tenuicolles from the mesentery of the 

 sheep, Cist, cellulosa from the muscles of the swine, Ccenurus cere- 

 bralis from the brain of the sheep, the same form of Tcenia, viz. 



1 VAN BENEDEN Ann. des Sc. natur. Sdrie in. Zoolog, Vol. xx. pp. 320, 321, 



2 VON SIEBOLD Band u. Blasen-vriirmer, 8vo. Leipsig, 1854, p. 106. 



