THE BEHAVIOR OF OTHER INFUSORIA 



I2 5 



tion (•'orientation") may be brought about by the selection of varied 

 movements. 



The common hypotrichan Oxytricha Jallax, abundant in vegetable 

 infusions, is well fitted for the study of this reaction. A large number of 

 specimens are placed on a slide or trough. When one end of the trough 

 is gradually heated 

 by passing water at 

 a temperature of 

 40 degrees beneath 

 it, the Oxytrichas 

 at this end are 

 seen to become 

 very active, dart- 

 ing about in all di- 

 rections (Fig. 84). 

 As the temperature 

 rises, they give the 

 avoiding reaction, 

 — darting back- 

 ward, and turning 

 to the right. This 

 is alternated with 

 rapid dashes for- 

 ward. Whenever 

 a specimen passes 

 toward the warmer 

 end of the trough, 

 or when it comes 

 in contact with the 

 sides or end, it re- 

 sponds with the 

 avoiding reaction. 

 But a specimen 

 passing away from 

 the heated region, 

 in the direction of 

 the arrow at 14 



(Tig. 84), does not Fig. 84. — Reaction of Oxytricha to heat. The slide is heated at 

 give the reaction tne enc ^ *• An Oxytricha in position i reacts as indicated by the arrows, 

 i ... repeatedly moving backward, turning to the right, and moving forward, 

 Utcause ll IS pass- thus occupying successively the positions 1-14. When it finally be- 

 ing from a hot to comes directed away from the heat, as at 13-14, it ceases to change its 

 1 . rpi direction of movement, but continues to move straight ahead, thus 

 COOl region. 1 ne reaching a cooler region. 



