TRANSMIGRATIONS AND METAMORPHOSES. 



211 



which are no longer of use to them, decay ; and at one 

 of the extremities appears a crown of new hooks quite 

 different from the former ones, which will serve to 

 anchor their progeny in the new host into which they 

 may be introduced." 



Thus the vesicular worm (Fig. 50), fully formed, 

 and without undergoing any 

 change, waits till its host, or 

 the organ which shelters it, is 

 eaten, and then wakes up in 

 the stomach. Every living 

 cysticercus which penetrates 

 into the stomach, instantly 

 quits its torpid state ; it gets 

 rid of its useless parts, aban- 

 dons its former cavity, pene- 

 trates into the intestine, 

 attaches itself by its new 

 hooks and its suckers to the 

 enclosing membranes, and grows with such rapidity, 

 that in less than six weeks, we often find a tape-worm 

 many metres in length. The vesicle which had hitherto 

 protected it is abandoned, and the part which remains 

 with hooks and sucker is the mother which has produced 

 in this agamous manner the whole colony. This mother 

 is usually called the head of the taenia, or more properly 

 the scolex. As long as the mother is there, she engenders 

 and produces cucumerinse, that is to say, proglottides, 

 which are the perfect and sexual state, of the cestode. 



We have seen among the trematodes a worm of 

 a particular form leave the egg, and immediately 

 produce a swarm of young ones, which go and Jive 



Fig. SO.— Vesicular worm. 



