388 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



served. The original report from Rana esculenta I have not found 

 It is an old report. If correct in its identification of the Opalinid^ 

 the infection may perhaps have been but temporary. It is easy ex- 

 perimentally to infect temporarily tadpoles of almost any of the 

 European species of Anura with cysts of almost any European 

 species of Opalinid (see Metcalf, 1909 and Brumpt, 1915). There 

 is, however, a recent report (Andre, 1913) of this species in a Swiss 

 R. esculenta. The infection of Triturus may well have been to its 

 habit of eating tadpoles of Anura, though the apparently permanent 

 infections of the American Urodele Amhystoma tigrinum by Pro- 

 toofalina mitotica, found by Powers, makes the normal infection of 

 Triturus by Protoopalina intestinalis seem less improbable. The 

 reports from Australia of Protoo'paUna intestinalis in two species of 

 Hyla and in Uperoleia may very likely be based upon one or more 

 species similar to P. intestinalis but really distinct. It would indeed 

 be remarkable to find in these hosts and in Australia true P. intes- 

 tinalis^ but we have already noted indications of the long persistence 

 of Opalinids unmodified in their secluded and uniform habitat 

 (p. 356 et seq.). We can not, then, with entire confidence accept 

 Protoopalina intestinalis as a species which is regularly found in 

 hosts belonging to different families, though this may well prove to 

 be true. 



No species of Zelleriella is reported from more than one genus oi 

 host, except for the report of " Z. antilliensis or very similar forms " 

 from five genera of hosts belonging to two families. Probably more 

 careful scrutiny would show several species of Zelleriella to be in- 

 volved. Of the multinucleated forms, Cepedea dimidiata is unques- 

 tionably found normally in Rana and Bufo. Opalina ohtrigonoidea^ 

 or at least forms which in my study I am unable to distinguish from 

 this species, are found in two species of Bufo, three species of Hyla, a 

 Scaphiopus, a Gastrophryne, and in two species of Rana which are 

 closely similar to one another. It is, of course, possible that in some 

 ijistances the forms in the different families of hosts belong to distinct 

 species which are so similar anatomically that they can be dis- 

 tinguished only by experiment, but there seems no reason for think- 

 ing this to be probable. Opalina ranarum is found in Borribina 

 (rare), in two species of Bufo, and in four species of Rana, three of 

 which are closely similar. Opalina virguloidea is found in two 

 species of Hyla and in two species of Rana, which are similar to one 

 another. 



We thus see that two species of Opalinae angu^tae and one species 

 of Opalinae latae are each found in hosts belonging to different fam- 

 ilies. The same is true of one species of Cepedea. In contrast to 

 these multinucleated forms, we find among the binucleated Opahnids 





