118 



Host. Parasites. 



Bufo vulgaris 1 Opalina rananini 



variahilis I - • dimidiata 



Bombinator igneus Ì - caudata 



imchypus j - intestinalis 



I find by experiment that tadpoles of Rana esculenta. Bufo vulgaris 

 and Bombinator paclnjpus may each be readily infected with any or 

 with any two or with all three of the species Opalina intestinalis^ 0. 

 caudata^ 0. dimidiata, by feeding the cysts to the tadpoles. I have not 

 experimented with the cysts of 0. ranaru7ii, 0. ohtrigona or 0. xelleri. 

 Young and full-grown frogs of Rana esculenta are easily infected from 

 cysts of 0. intestinalis (I have not tried cysts of other species) : young 

 toads [Bufo vidgaris] ca,n be infected from cysts of 0. intestinalis and 

 0. caiulata (I have not tried cysts of other species), also adult Hyla 

 arborea can be infected from cysts and from adults of 0. intestinalis. 



Adult Opalinae, fed to tadpoles, are in part digested, but many 

 pass through the intestines unharmed and establish apparently thriving 

 colonies in the recta. I have infected tadpoles of Rana escidenta, Bufo 

 vulgaris ?cnà Bombinator pachypus each with adults of each of the follow- 

 ing species Opalina dimidiata, 0. obtrigoita, 0. caudata and 0. inte- 

 stinalis. It is probably true that tadpoles of any species can be infected 

 with either cysts or adults of any species of Opalina. I cannot yet say 

 whether the Opalinae thus introduced to an unnatural host will con- 

 tinue to live longer than four weeks, but they grow and thrive for that 

 length of time and probably live indefinitely. It seems probable that 

 such cross infections occur frequently under natural conditions. Why, 

 then, do we find the distribution of the several species of Opalina in 

 the different frogs and toads so restricted? The cysts introduced into 

 an unnatural host hatch , the little animals which emerge dividing and 

 forming gametes which conjugate. 



For our knowledge of Opalina we are indebted chiefly toZeller's^ 

 beautiful paper and to I^eresheimer's^ very interesting preliminary 

 note. I have made no attempt to discuss either of these, or any other, 

 papers, referring only to a few disenpancies between my work and 

 Neresheimer's. 



AViirzburg, July 1^11907. 



- Zell er, E., Untersuchungen über die Fortpflanzung und die Entwicklung 

 der in unsern Batracliiern schmarotzenden Opalinen. Zeitschr. f. wiss. Zool. 

 Bd. XXIX. 1877. p. 352—379. 



3 Neresheimer, E., Der Zeugungskreis von Opalina. Sitzgsber. d. Ges. f. 

 Morph, u. Phys. in München. 1906. Hft 1. Read July 15th 1906. 



