Holophryidae 99 



the several culture methods that have been suggested since the time of 

 Putter's first studies provide the first two desiderata mentioned. The 

 third can perhaps be secured by frequent transfer of the animals to new 

 culture fluid. Supplying predigested food or foods may not prove diffi- 

 cult. On the other hand, to keep the culture free of oxygen is not a 

 simple problem. It requires a technique not yet developed, so far as I 

 know, for culturing any protozoan, except such as will thrive within an 

 agar or gelatin medium. Frequent changing of cultured opalinids to 

 fresh culture fluid without introduction of considerable oxygen by ex- 

 posure to the air involves still greater technical difficulty. It could doubt- 

 less be done with the aid of a gas mask in an oxygen-free room. 



Protoopalinae, when kept in Putter's or Locke's solution, either with 

 or without bits of the rectal wall of the host, show signs of abnormality 

 within a few hours, often within 4 hours or so. These facts, and the 

 further fact that in this country Protoopalinas are available for study 

 only in a few regions and in the northeastern states not at all, have made 

 me hesitate to attempt to develop a culture medium and culture methods. 

 On the other hand, given a suitable culture medium and procedure, the 

 prompt response by Protoopalina by visible cytological changes under 

 unfavorable conditions might render Protoopalina a peculiarly favorable 

 test animal for studies of protozoan physiology. 



References 

 For Opalina ranarum see p. 69. 



Bibliography 



Konsxjloff, S. 1922, Untersuchungen iiber Opalina. Arch. f. Protist. 44:285. 

 Larson and Allen, 1928. Further studies on the reaction of Opalina to various 

 laboratory culture media. Univ. Kansas Sci. Bull. 18:8. 



M. E. D. 



Order holotrichida, Family holophryidae 



CULTURE MEDIUM FOR THE CILIATE LACRYMARIA* 



MAST, who has had wide experience in collecting Protozoa, says 

 (1911, p. 230) : "Lacrymaria is relatively scarce in nature. It is 

 occasionally found in cultures containing decaying aquatic plants but 

 never in great numbers. One rarely finds more than two or three speci- 

 mens in a drop of solution." No one has succeeded heretofore in culti- 

 vating it in the laboratory. 



Malted milk in distilled water was prepared in two sets, one of which 

 was boiled and the other not. Both were seeded with Lacrymaria and 



* Abstracted from a paper in Science 63:212, 19:6, by Y. Ibara, Johns Hopkins 

 University. 



