332 



PLATTHELMINTHES. 



water, and thence pass in the food into the stomach usually of 

 herbivorous or omnivorous animals. As soon as the egg membranes 

 are digested or burst by the action of the juices of the stomach of 

 the new host, the embryos which have been thus set free bore their 

 way into the gastric or intestinal vessels by means of their six 

 (rarely four) hooks, the points of which can be approached and 

 removed from one another over the periphery of the small globular 

 embryonic body. When they are once within the vascular system, 



FIG. 2G9. a, Brood-cp.psule of Echinococcus with developing heads (after E. Leuckart). I, 

 Brood-capsule of Echinococcus (after G. Wagener). c, Heads of Echinococcus still connected 

 with the wall of the brood-capsule one is evaginated ; Vc, excretory canals. 



they are no doubt carried along passively by the current of blood, 

 and transported by a longer or shorter route into the capillaries of 

 the different organs, as the liver, lungs, muscles, brain, etc. After 

 losing their hooks, they usually become enveloped by a cyst of 

 connective tissue, and grow into large vesicles with liquid contents 

 and a contractile wall (fig. 268). The vesicle gradually becomes a 

 cystic or bladder worm by the formation of one (Cysticercus*) or 

 * Exceptionally two or more heads are found in some Cysticercus forms. 



