THE OPALINID CILIATE INFUSOEIANS. 87 



different individuals of the same species, though these differences 

 are apparently within definite limits for each species. But the ex- 

 treme interval measurements in one species may be overlapped by 

 the extreme measurements in another species which has a different 

 mean. Measurements of tlic cilia line interval do not help us much 

 in determining species. The size and shape of the endospherules 

 seem to be fairly constant for most species, and the size and shape 

 differ enough with the species, in some instances, to be of some 

 assistance. Chromosome number, when discernable, is a definite 

 character, but the study of this feature requires well-preserved ma- 

 terial, better preserved than most of that I have obtained from 

 museum specimens of Anura. 



It is evident that to review successfully the taxonomy of the 

 Zelleriellas one should have data from the whole life cycle of each 

 species. I have not any such complete material. The studies here 

 recorded are confessedly inadequate and the conclusions reached only 

 tentative. In numerous instances I shall make no attempt to de- 

 termine definitely the species and will leave the forms unnamed, 

 merely referring them to their hosts and leaving the naming of the 

 forms to be done after some future study of more complete material. 

 In such cases the organism will usually be referred to merely as the 

 ZeUeriella of its named host, as for instance, ZellerieUa [of Bufo 

 woodhousi], the ZellerieUa found in Woodhouse's toad, or Zelleri- 

 eUa opisthocai^a [of Bufo typhonius], the form of Z. opisthocarya 

 found in Bufo typhonius. This method of designation is an awk- 

 ward one, but is adopted because the terms used can not be treated 

 by others as true taxonomic names. Their awkwardness will thus 

 prevent future confusion. In a few instances, where there is greater 

 probability of the species being valid, I give a tentative name, but 

 inclose it in brackets to indicate that the name is only provisional 

 and should not yet be recognised, as, for instance, ZeUeriella [engys- 

 tomopsis']. Such bracketed names are not to be taken as true tax- 

 onomic terms, but are provisional and merely a convenience for ref- 

 erence, to avoid circumlocution. If quoted by others the brackets 

 also should be quoted, unless the subsequent author wishes to assume 

 responsibility for validating the name. 



ZELLERIELLA HYPOPACHEOS, new species. 



Type. —United States National Museum Cat. No. 16461. 



Host. — Hypopachus vaj^olosus (Cope), one infection, in United 

 States National Museum specimen No. 24830, 35 mm. long, from 

 Guatemala; H. Hogue, collector; no date. 



