REACTIONS OF OPALINA RAN ARUM 331 



around in the chemical for some time would respond when 

 encountering the culture medium. 



Opalinas collected about acids introduced into the alkaline 

 culture medium. Opalina is more susceptible to hydrochloric 

 than to acetic acid. In one case, it was noted that Opalina 

 lived in .01% solution of acetic acid for fifteen minutes before 

 it proved fatal. Opalina reacts positively to nitric, sulphuric 

 and formic acids. Even when acids were quite concentrated, 

 it does not give avoiding reactions. The concentrations used 

 varied from N-500 to N- 10,000. 



Opalina avoids neutral salts and those exhibiting basic prop- 

 erties. If a .2% solution of sodium chloride is added to the 

 medium, Opalina, like Spirostomum (Jennings, '00) will avoid 

 it by turning to the right and swimming off in a new direction. 

 Opalina also responds by the avoiding reaction to a .005% 

 solution of potassium hydroxide. It also is negative in its reac- 

 tions to .02% to .002% solutions of each of the following salts: 

 ammonium chloride, calcium chloride, potassium chloride, and a 

 similar per cent solution of sodium hydroxide. In one case in 

 which calcium chloride was used the strong repellent action was 

 particularly noticeable; a large number of individuals, near the 

 salt, moved away and crowded together at the opposite end 



of the slide. 



TEMPERATURE 



Unlike Paramoecium and Oxytricha, Opalina does not give 

 the avoiding reactions to change in temperature. As Verworn 

 ('89) observed, it swims indifferently from a warmer to a colder 

 area and vice versa. If a quantity of culture medium, heated 

 to about 40° C, is put on one end of the slide, Opalinas coming 

 in contact with the warmer liquid swim actively about. When 

 they approach the center of the heated area, motion ceases 

 entirely, the cilia continue to vibrate rapidly for a few minutes, 

 and then stop beating; the entire animal soon disintegrates. 

 That Opalina is not very resistant to heat is shown by the fact 

 that if it is allowed to remain in a temperature above 22° C, 

 it dies in a short time. If Opalina is dropped into a heated 

 medium, it does not respond by the avoiding reaction as has 

 been observed in Pleuronema (Jennings, '06). Opalina shows 

 a very great resistance to extremely low temperatures. It does 

 not react to water at 2° C. 



