CHAPTEK IX. 



PARASITES THAT UNDERGO TRANSMIGRATIONS 

 AND METAMORPHOSES. 



A CERTAIN number of parasites establish themselves 

 at first in an animal which serves as a creche, then in 

 a second which serves as a lying-in hospital. This 

 passage from one animal to another is described under 

 the name of transmigration. In general, the entire 

 creche with its nurslings passes into the lying-in 

 asylum. The creche is always represented by an animal 

 which feeds on vegetable diet, which is destined for one 

 which is carnivorous : the lying-in asylum is represented 

 by the latter. The mouse is the creche which will pass 

 with all its clients into the cat which eats it. 



If we were treating of plants, we should say that in 

 the first host they are develojDed, and in the second they 

 blossom. The plant, like the animal, is agamous as long 

 as the flower and the sexual organs have not made their 

 appearance. 



The animal which migrates usually undergoes a com- 

 plete change in passing from one abode to another ; it is 

 agamous in the first instance, that is to say, without 

 sex, swathed and covered with a padded cap like a nurs- 

 ling ; in its last stage it is, on the contrary, endued with 

 all its sexual attributes. 



