200 ANIMAL PARASITES AND MESSMATES. 



intestines literally full of these parasites. We have 

 noticed the species which regularly frequent our bats, 

 and it only remains to discover the insects by means of 

 which they are introduced ; for it is probable that these 

 insects are infested by cerearise during the time that they 

 inhabit the water. Larvas and their parasites ought to 

 be carefully studied in the localities where bats abound. 



There are few birds, especially among the grallas and 

 the palmipedes, which do not enclose in their intestines 

 a certain number of distomes. The same may almost 

 be said of reptiles and batrachians, but it is especially in 

 fishes that their number is greatly increased. We may 

 say that there is no fish which does not nourish some of 

 these trematodes. Among a portion of these, the cycle 

 of evolution and transmigration ^is perfectly known ; we 

 may instance the Distomum nodulosum. This worm 

 inhabits the intestines of the perch. 



The scolex, as well as the cercaria, has its particular 

 characters, and we have long since found the latter in 

 a fresh-water mollusc, the Paludina impura. The cercaria 

 is easily recognized by the presence of two particular 

 folds at the base of the buccal bulb, and by the trans- 

 parency and the form of the extremity of the urinary 

 apparatus. In the adult distome, this same part of the 

 urinary apparatus encloses large vesicles with very dis- 

 tinct partitions. 



We may also mention among the distomes a species 

 from fish, which has a great affinity with the singular dis- 

 tome observed by Bilharz, of which we have spoken above. 

 This distome inhabits the "castagnole," or Brama rail. 

 Under the opercula of this fish, the skin is folded, and 

 forms one or more pouches, in each of which lives a 



