78 ANIMAL PARASITES AND MESSMATES. 



cages clean, and to remove dung and filth. Many 

 animals perform this office. The rectum of frogs is 

 always literally full of Opalinse which swarm in this 

 cavity, like ants in their ant-hill, and doubtless live on 

 the contents of the intestine. 



These Opalinae are true infusoria, which do not wait 

 till the fecal matters are decomposed, and till the waters 

 are corrupted by their presence ; they prevent accidents 

 which might arise, and interfere in time to purify the 

 water from these excretions. There have been found 

 hitherto in the rectum of frogs, and in the different 

 annelids, the Pachydrili, the Clitelides, the Lumbriculi, 

 and the Enchytrei. We have also seen them in the 

 Planaria and the Nemertians. There is no sight more 

 curious for those who are commencing microscopical 

 studies, than the examination of the contents of the 

 rectum of these Batrachians. Yan Leeuwenhoeck knew, 

 two hundred years ago, those animalculae, to which 

 Bloch at a later period gave the name of Chaos intesti- 

 nalis. There are also some Eotatoria, the AlhertidB for 

 example, which ought to have a place here, and which 

 Dujardin has described and named. They live in the 

 intestines of the Lumbrici and of snails, and in the 

 larvae of Ephemerides. 



Dujardin first pointed out the Albertia vermiculus ; 

 since then Mons. Schultze has made loiown the Albertia 

 of the Ndis littoralis, and Eadkewitz has recognized in 

 the small worm of our gardens the Enchytreus vermicu- 

 laris. Long since, Siebold correctly stated that these 

 animals are not parasites, since they do not live at the 

 expense of their host. 



There is a worm in the Philippine Islands, as Pro- 



