THE-OPALINin CILIATK IXFUSORIAXS. 



245 



Adult Rana clamltans have yielded no Opalinids, though 33 speci- 

 mens from 8 localities have been examined. Professor Hegner, of 

 the Johns Hopkins University School of Hygiene and Public Health, 

 sends me a slide, a smear preparation from a tadpole of what seemed 

 to be Rana clamitans^ containing numerous Opalinas all of the sort 

 shown in figure 221. These are distinct from any Opalina as yet 

 seen. They are very broad, almost circular in form, but each in- 

 dividual bears posteriorly a short, curved, sharp-pointed pro- 

 tuberance. [See Opalina coracoidea, p. 234.] The shape of the body 

 seems to demarcate sharply this Opalina from any other speries. but 



Fig. 221. — Opalina [laevarum] : a, b, and c, magnified 460 diametebs ; d, magnified 



1,000 DIAMETEBS. 



as the 3^oung individuals of many species have never been observed, 

 it is unsafe to name the present species definitely from the very young 

 specimens which are the only ones available for study. The sharp, 

 curved, posterior point suggests that this Opalina may be one of the 

 western hemisphere narrow species, even though its body in this 

 young stage is very broad. Young Opalina hylaxena, from the tad- 

 poles of H'yla versicolor', are almost as broad as the specimens of 

 O. [lai'va'Tuni], though the adults of O. hylaxena are elongated and 

 slender. It is highly probable that this Opalina from the Nova 

 Scotian tadpoles is a distinct species, but it is best to name it only 

 tentatively. The identification of the species of the host is somewhat 

 uncertain. 



