STERELMINTHA. 



Fig. 34. 



during the life of the creature, are visibly capable of sponta- 

 neous contractions on the application of stimuli. To this bladder, 

 or common body, are appended numerous heads, or rather mouths, 

 which are individually furnished with an apparatus of hooks and 

 suckers, (Jig. 33, 2, a, &,) calculated to fix them to the surrounding 

 tissues, whence they derive nourishment. 



(111.) The Cysticerci, or common hydatids, agree in the main 

 features of their structure with the Ccenurus, but are provided 

 with only one head or oral orifice resembling those of Coenurus 

 (Jig. 34; 2). These 

 animals are found in 

 almost all the viscera of 

 the body ; and not un- 

 frequently, especially in 

 pigs, exist in great num- 

 bers, not only in the 

 liver, which is their most 

 usual seat, but in the 

 cellular texture of the 

 muscles, and even in 

 the eyes themselves. 



The human frame is not 



free from their ravages, 



and, when they abound, 



serious consequences 



frequently result from 



their presence. 



The Cysticercus 



crassicollis is less fre- 

 quently met with than 



the ordinary hydatid (C. tenuicollis). In this animal the head 



is provided with a prehensile apparatus analogous to that found 

 the last described species ; a structure which resembles pre- 



in 



cisely what we shall afterwards find in the Tcenice or tape-worms, 

 with which these creatures are closely related in a zoological point 

 of view. Even in external form they are allied to the cestoid 

 worms, as may be seen in the annexed figure, in which, notwith- 

 standing the vesicular character of the posterior part of the body, 

 the anterior portion is distinctly divided into segments. 



(112.) The mode of reproduction in these entozoa resembles 

 that of the Volvox globator. They propagate by internal gem- 



