OPALINID CILIATE INFUSORIANS METCALF 



551 



lating processes." It appears slightly truncated or rounded at the 

 anterior end, and tapers gradually along the "undulating processes" 

 toward the pointed posterior end. The length of the body is about 

 4 times the greatest width. 



Cilia bordering the anterior part are slightly longer than those 

 found at the posterior region. The ectosarc, which has a vacuolated 

 appearance, is rather thick as compared with that of the other species 

 of Opalina. In addition to the nuclei, there are many small spheri- 

 cal or elongate-oval endospherules in the endosarc. 



Opalina undulata is quite different from 0. spiralis Metcalf (1923a) 

 in its plicated manner of the posterior half of the body. In the 



Figure m.-Opalina undulata Nie from Rana limnochaTts, X ca. 300. (After Nie.) 



latter species the spu-als are rather irregular in shape and number 

 and it shows no ' 'undulating processes' ' as observed in the present species. 

 The broader anterior portion (130-140/.) and the smaller size of the 

 nuclei (4 3-4.7m) also serve to distinguish 0. spiralis from 0. undulata. 

 Measurements, in microns: The body length varies from 182 to 

 378, the width from 44.8 to 105; the average diameter of the nuclei 

 is 5.7, and the average diameter of endospherules is 1.5. 



