PARASITES FREE WHILE YOUNG. 



161 



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

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

 spermias. Fig. 34 represents one of these sacs of Pso- 

 rospermiffi from a cephalopod. 



The gregarinffi Kve in their perfect form chiefly in 

 insects, crustaceans, and worms. Fig. 35 

 represents a gregarina very common in 

 the hbellulae. 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 gregarinae ; it lives in the testicle, as 

 well as in the sahvary cells, of a plana.ria, 

 the Mesostomum Ehrenbergii; Schneider 

 represents the various phases of its de- ^iU^^^S^K 

 velopment. In the autumn of 1871, nearly i^^'^aofthe Agrion. 

 all the mesostomes perished through the presence of 

 these parasitical organisms : in the following year they 

 were rare. 



Some years ago, Kolhker 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 Bicyema. 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. 



