. PARASITES FEEE WHILE YOUNG. 



161 



the mechanism by which it moves (Fig. 33.) While 

 young they are encysted, and bear the name of Psoro- 

 spermise. Fig. 34 represents one of theBe sacs of Pso- 

 rospermise from a cephalopod. 



The gregarinse live in their perfect form chiefly in 

 . insects, crustaceans, and worms. Fig. 35 

 represents a gregarina very common in 

 the libellulse. The largest species inhabits 

 the intestines of the lobster. My son has 

 studied them very carefully, and pub- 

 lished the results in the bulletins of the 

 Academy of Belgium. 



Schneider has described a parasite 

 which ought, no doubt, to be placed among 

 the gregarinse; it lives in the testicle, as 

 well as in the salivary cells, of a planaria, 

 the Mesostomum Ehrenbergii; Schneider 

 represents the various phases of its de- ^;2SS 

 velopment. In the autumn of 1871, nearly lar ™ ofthe A «™«- 

 all the mesostomes perished through the presence of 

 these parasitical organisms : in the following year they 

 were rare. 



Some years ago, Kolliker discovered on the spongy 

 bodies of molluscs, certain parasites, the nature of which 

 appears still as enigmatical as on the first day of their 

 discovery. The Wiirzburg professor gave them the name 

 of Dicyema. We have had for a long time in our portfolio 

 some observations upon them, and at the close of the 

 chapter " On Parasites that undergo Transformations," 

 we give a representation of a Dicyema which we found in 

 abundance on the Sepia officinalis off the coast of Belgium. 



