OPALINID CILIATE INFUSORIANS — METCALF 489 



with some adult toads, were many tadpoles; of those examined sev- 

 eral bore interesting small Zelleriellas, with tails developed to dif- 

 ferent degrees, but none were found of fully adult shape. In one 

 smaller tadpole were Zelleriella larvae in the Proioopalina stage and 

 other cells that perhaps were stages in the development of male 

 gametes. 



Figure 43 shows free-hand sketches from living parasites or non- 

 permanent preparations from tadpoles of B. crucifer. They resemble 

 Protoopalinas of what I have considered the most archaic subgeneric 

 group. They have elongated posterior ends, slender, unciliated, and 

 sharp-pointed. One, not drawn, shows two nuclei still united by a 

 thread after division. Another shows a single nucleus with several 

 axial excretory vacuoles in front of and behind it. These individuals 

 may represent Zelleriella larvae in a Proioopalina stage or they may 

 be stages in the development of male gametes. These forms from 

 the tadpole host were studied with a magnification of 1,010 diameters 

 after staining with acetocarmine and were not kept. 



Of 28 adult specimens of Leptodadylus ocellatus from Rio de Ja- 

 neiro, 15 bore no opalinids, 13 were infected with large or small Zel- 

 leriellas. Fourteen of these frogs had been in captivity for six weeks 

 or more, and on this account the opalinids may have disappeared 

 from some of them. Some of the parasites were Z. uruguayensis, 

 some Z. brasiliensis, a few were Z. antunesi, and some were inter- 

 mediate, such as I am calling forma guadrata. In one individual 

 typical Z. brasiliensis and Z. antunesi were present, their nuclei 

 being large in antunesi and small in brasiliensis. This is one of the 

 few instances in which I have found in one individual host what seem 

 to be two species of opalinids. 



The conditions of parasitism in Leptodadylus ocellatus, Bujo dor- 

 bignyi, B. crucifer, and B. arenarum, both in Brazil and in Uruguay, 

 are very puzzling. There are large Zelleriellas with large nuclei 

 {''uruguayensis"), small Zelleriellas with nuclei of half the relative 

 size ("brasiliensis"), tailed forms ("antunesi") with nuclei of the 

 relative size found in "uruguayensis," and posteriorly truncate forms 

 ("guadrata") with nuclei relatively large. Through guadrata forms 

 antunesi seems to grade into Z. uruguayensis but not into Z. brasi- 

 liensis. 



ZELLERIELLA DUBIA, new species 



Figure 44 



Type: U.S.N.M. No. 22630. 



Host: Eupemphix nana Boulenger. Three specunens from Angra 

 dos Reis, State of Rio de Janeiro, Brazil, showed no opalinids; three 

 were heavily infected. 



