ANIMAL PAEASITES. 21 



the caudal vesicle, and this because the worm must first care for 

 its habitation, and prepare this in proportion to the growth of its 

 caudal vesicle. 



3. In the vesicle the body sits, but internally, and, as it were, 

 turned inside out. It must therefore live upon its own juices in 

 the vesicle, until it is time to reverse itself, because it already has 

 the four suckers and the circlet of hooks upon the head. (See his 

 figure, tab. xix.) The caudal vesicle thus serves it as a reservoir 

 of nourishment. 



4. When its body has attained the necessary degree of deve- 

 lopment, and the vesicle over it is large enough 1 for its habitation, 

 the body reverses itself by the agency of its folds and segments, 

 from within outwards, and then constantly grows until it reaches 

 its perfect form and size, such as we procure it from the cysts of 

 the liver. 



5. The body here sits still in the vesicle, exactly in the same 

 way that the numerous bodies of the cystic tape-worm of the 

 sheep sit in the interior of their common vesicle in the manner of 

 a colony" 



Goeze, or, more correctly, his friend Wagler, also proposes 

 (1. c., p. 292) that the Tcenia of cold-blooded animals should be 

 transferred (by feeding) into cold- and warm-blooded animals, 

 and those of warm-blooded animals into warm- and cold- 

 blooded ones, and watched to see whether they remained the 

 same or became degenerated, and acquired other properties from 

 the difference of their host, from what they had in their original 

 situation, like certain cultivated plants. Lastly, like Pallas, he 

 recommended the administration of the eggs of Tteni<p to animals 

 (1. c., p. 290). The views of Pallas and Goeze were also followed 

 by Steinbuch and Fischer. 



With this the progress of the theory of the cystic worms 

 ceases for more than half a century, and with Zeder and Ru- 

 dolphi a general retrogression commences. Zeder, in 1803, in 

 his ' Naturgeschichte der Eingeweidewiirmer/ formed a distinct 

 family of the cystic worms ; Eudolphi constituted them a 

 separate order (' Entoz. Synops./ 1819, p. 536), and thus, 

 although he pointed out the resemblance between certain species 

 of cystic worms and the Tanice, separated them in point of 



1 This seems to be a misprint ; it should probably be " the vesicle is no longer large 

 enough." 



