326 ELSA SHADALL 



tion the work was done. Practically all material used was 

 obtained from the rectum of leopard frogs, Rana pipiens, which 

 were kept in a tank of running water in a vivarium. Although 

 the room was heated, the temperature of the water ranged from 

 2° to 10°C. 



Zeller ('76) observed that large Opalinas seemed to be absent 

 from frogs in the month of January. This might be the case if 

 frogs are allowed to remain in their natural habitats. During 

 the present observations, however, Opalinas were apparently 

 normal throughout the winter, though all frogs examined were 

 not infected. Dobell ('07) pointed out that lack of food and 

 increase in the number of bacteria in the rectum of the frog 

 were causes of degeneracy in Opalina. In several instances, the 

 writer noted that Opalinas were not found when there were no 

 faeces or when the bacteria were few iri number. The largest 

 numbers were obtained when there was a considerable quantity 

 of faeces and when the number of bacteria was comparatively 

 large. 



Material for observation was usually obtained from a frog by 

 pithing or quickly chloroforming it. Putter's saline medium, 

 already mentioned, or a physiological salt solution made suit- 

 able culture media except when chemical stimuli were used. 

 In the latter cases, it was found that by forcing water down the 

 alimentary tract of the frog, a sufficient amount of liquid to 

 serve as a medium for observations could be obtained without 

 interfering with the normal activities of the Opalinas. When 

 the medium was ready for use, enough was dropped on an 

 ordinary slide to nearly cover one-half of it. If another liquid 

 was introduced, it was carefully added with a dropper drawn 

 to a fine point. Frequently the drop of chemical was placed 

 next to the medium containing Opalinas, and then by the aid 

 of a needle, was induced to flow across gradually. Experiments 

 with colored liquids showed that diffusion took place quite 

 slowly and that sometimes the introduced drop remained in 

 only a small portion of the medium. A cover glass was usually 



not used. 



OBSERVATIONS ON LOCOMOTION 



Considering the environment of Opalina, it may be justly 

 called a comparatively active creature, especially immediately 

 after division. Other investigators have noted that the smaller 



