27 



" 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 its head. The 

 caudal vesicle thus seems as a reservoir of nourish- 

 ment. 



" 4. When its body has attained the necessary de- 

 gree of development, and the vesicle over it is no 

 longer large enough for its habitation, the body re- 

 verses 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 tapeworm of the sheep sit in the interior of 

 their common vesicle, in the manner of a colony" 

 (Kiichenmeister). 



Still the development was not followed out until 

 Steenstrup, of Denmark, by his " Theory of the Alter- 

 nation of Generation," in 1842, supposed that these 

 cystic worms were early steps in the development of 

 the generation of Hehninthes. Dujardin, of France, 

 in 1845, in his " Histoire Naturelle des Helminthes," 

 pp. 554, 633, and Von Siebold, of Germany, in the 

 second volume of Hud. Wagner's " Handbuch der 

 Physiologic," art. Parasiten, were the first who stated 

 that these cystic worms were undeveloped animal 

 forms, and young states of tapeworms ; and, indeed, 

 that they were produced from those germs of tape- 



