THE BEHAVIOR OF OTHER INFUSORIA 113 



To most very intense stimuli Euglena responds by contracting into 

 a sphere and beginning to encyst. 



The behavior of most other flagellates is not known in detail, since 

 the organisms are usually very minute and their precise movements can 

 be followed only with much difficulty. Cryptomonas ovata is known to 

 respond to stimuli in essentially the same way as Euglena (Jennings, 

 1904 a), the swerving being toward the more convex surface. The 

 flagellate swarm spores of various algae react in much the same way, as 

 is shown by the descriptions of Naegeli (1860) and Strasburger (1878), 

 though the precise details have not been worked out as they have for 

 Chilomonas, Euglena, and Cryptomonas. Naegeli (/. c.,p. 101) describes 

 the behavior of the flagellate swarm spores on coming against a mechani- 

 cal obstacle, as follows: They swim backward, turn to one side, then 

 swim forward in the changed direction. This is exactly what Chilo- 

 monas does, as we have seen. Similar observations have been made 

 on flagellates by various investigators, but only in the species we have 

 named has the side toward which the organism turns been determined. 



B. Ciliata 



In many free swimming ciliates the action system is known to be 

 essentially similar to that of Paramecium. All swim in spirals, swerv- 

 ing toward a certain side, and react to stimuli by backing and swerving 

 more than usual toward a structurally defined side. Loxodes rostrum 



FIG. 75. Reaction of Loxo- FIG. 76. Methods of reaction to strong stimuli 



phyllum meleagris. 1-4, succes- in Stentor. The individual at i is stimulated ; it there- 



sive positions. upon swims backward (2, 3), turns toward the right 



aboral side (3, 4), and swims forward (5). 



in reacting turns toward the aboral side. Loxophyllum meleagris re- 

 acts as a rule by turning toward the oral side (Fig. 75). Stentor poly- 

 morphus, Stentor caruleus, and Stentor rceselii (Fig. 31, 6), when free 

 swimming, react by turning toward the right aboral side (Fig. 76). Bur- 

 saria truncatella reacts to most stimuli by swimming backward and 



