DISTRIBUTION. 



109 



In an enumeration of those animalcules whose distribution pertains 

 to neither of the two last-named elements, but is for the most part 

 inextricably interwoven with that of various more highly organized animal 

 types, upon whose vital juices they arc dependent for their existence, 

 the most prominent position has undoubtedly to be awarded to the 

 mouthless Opalinidae. All of the various specific and generic types of 

 this important family group are found leading an endoparasitic existence 

 within the alimentary canals, in some instances of various Amphibia, such 

 as newts, frogs, and toads, and in others of various aquatic Annelida, these 

 latter being in several instances marine. Among the Peritricha, the two 

 genera Ophryoscolex and Entodiniuni are notable for their limitation to 

 the stomachal cavities of various ruminants, while the Heterotrichous form 

 Balantidiiim coli honours the rectal passage of the human subject with 

 its presence. Other species belonging to the last-named genus, as also 

 its near allies Plagiotoma and Nyctotherus, limit their attentions in a 

 similar manner to various worms and other lower Invertebrata. The two 

 generic types ConchopJithirns and PtycJiostomum form noteworthy examples 

 of the parasitic series, being both found inhabiting the mucilaginous 

 body-slime of various terrestrial Mollusca. The more recently discovered 

 Ichthyophthiriiis undtifiliis is remarkable for its attachment to the cuticular 

 surface of young trout, and often causes severe losses to the French fish 

 cultivators by reason of its depredations. 



Although the Tentaculiferous section of the Infusoria yields but few 

 examples of endoparasitism, one single genus, SpJiccrophrya, is characterized 

 by its passing the earlier stages or chief portion of its existence within the 

 internal substance or endoplasm of various other animalcules. The Flagelli- 

 ferous section of the class yields, so far as endoparasitic habits are con- 

 cerned, a series of examples little inferior in extent and interest to that of 

 the Ciliata. It is to the ranks of this group that have to be assigned the 

 actively motile organisms recently discovered by Mr. T. R. Lewis in the 

 blood of healthy rats, and described hereafter under the title of Hcrpenionas 

 Leivisi. One species of Trichomonas has as yet been found only in fluid 

 obtained from the human vagina. Bodo tirinariiis inhabits human urine, 

 while the several species of Lophouioiias infest the intestinal tracts of the 

 cockroach and other Insecta. The two specific forms here referred to the 

 order of the Trypanosomata undoubtedly represent the Flagellate Protozoa 

 in their most rudimentary condition, and are respectively inhabitants of 

 the blood of frogs and other Amphibia, and the rectal passages of ducks, 

 geese, and other domestic poultry. As intimated in the systematic de- 

 scription of these types, it is possible that they represent developmental 

 conditions of the same organism.* 



Apart from the large number of Infusoria that exhibit ecto- and 

 endoparasitic habits, it will be found that a very considerable series, while 



* An extensive notice of the essentially parasitic representatives of the Infusoria is embodied in 

 an article contributed by the present author to the ' Popular Science Review' for October 1880. 



