1913] Gee: Behavior of Leeches 263 



ulus may gradually be increased until the leeches in many cases 

 will fail to respond to a considerable shock of the springboard. 

 However, there is a limit to the degree of stimulation to which 



Acclimatization to Jars as Expressed in Number of Seconds Cessation 

 OF Undulatory Movements in a Single Specimen of Diva microstoma 



they will continue to respond by acclimatization in their rhyth- 

 mical response, and as the result of a transgression of these limits 

 reactions of the type above described, such as looping, swimming, 

 feeling movements, or reversal of geotaxis may take place. The 

 accompanying table (see table V) serves to show the range of 

 individual variation in the responses of five leeches. 



2. Acclimatization to Successive Shadows 

 If the leeches, while their posterior suckers are attached to 

 the under surface of a stone, are exercising undulatory move- 

 ments, and a black cardboard of fair size is brought between 



