46 



DEVELOPMENT OF CESTODES. 



EcMnococcus (fig. 14). These structures, so formed, may live 

 in an animal for a very considerable time ; but unless they are 

 taken into the body of some other animal, they must eventually 

 die. Should a carnivorous or insectivorous animal, or such an 

 omnivorous one as the pig, or even man, devour in the meat 

 that they eat any of these cystic forms, the action of the gastric 

 juice, again acting upon the cestode, dissolves the walls of 

 the "bladder," and releases the rudimentary scolex or scolices 

 formed in it. These heads of future tapeworms then pass into 

 some portion of the intestine, and by means of the hooks with 



. -S ,/ 



- -.f- J 



Fig. 11. — Two forms of Cysts uf Cestodes, 



^, A Ci/s^tcez-CTw (after Neumann), b, ACosnurus. 

 s, scolices ; i, cavity of cyst. 



which they are provided, and augmented by the suckers, they 

 anchor on to the lining mucous membrane of the small and 

 large intestines. As soon as the embryo has taken up its abode 

 on the mucous membrane the scolex commences to bud off 

 segments, formed by an asexual budding in the longitudinal 

 axis, and resulting in the formation of a mature sexual cestode 

 or tapeworm, which may in some species reach as much as thirty 

 feet in length. At one time tapeworms were considered colonial 

 animals, each proglottis being a distinct individual; but since 

 it is the scolex which grows, we must consider that the whole 

 is an individual, and that the individuality of the proglottis is 

 subordinate to it,— and, moreover, we find one excretory and one 

 nervous system common to the whole. 



