1913] Gee: Behavior of Leeches 223 



In the experiments on Dina, the capillary rod was pushed 

 to the bottom of the dish, while the animal was displaying the 

 deceptive quiet reaction, about an inch from the anterior end of 

 the leech, and moved slowly towards it. When the rod came 

 close to the body the animal responded by turning towards it, 

 immediately recoiling upon contact. Even to this slight stimulus, 

 if repeated similarly, the animal will often reverse the direction 

 of its movement by a sharp turn. 



Place a number of individuals attached to the under surface 

 of a stone in an aquarium near a window and allow them to 

 remain undisturbed for some time. The anterior third to half 

 of the body will be extended from underneath the stone, and 

 undulatory respirator}' movements executed. If some dark ob- 

 ject, such as a large piece of cardboard, be interposed between 

 them and the window, the undulatory movements will immedi- 

 ately cease, the animal hugging the bottom of the dish. Allow 

 this to remain, or remove it, as you like, and in many cases the 

 animal will quietly resume its undulatory movements. To a 

 very slight jar of the table or dish the same type of response is 

 given as to the shadow. The leech is an extremely sensitive 

 animal, and, as pointed out by Whitman (1898), unless consid- 

 erable care is exercised, oftentimes, the experimenter is likely 

 to overlook this fact, since the leech is aLso an animal capable 

 of withstanding conditions involving severe tests of vigor, as will 

 be shown in a succeeding portion of this paper. 



5. Reactions to Light 

 The leeches studied were found to show a marked negative 

 phototaxis. Upon their being brought into the laboratorj' and 

 placed in a long glass dish facing the window it was a matter 

 of only a few minutes before the major portion of them had 

 made their way to the less illuminated part of the dish. A 

 similar reaction was secured in response to the stimuli of a 

 60-watt and of a 100-watt Mazda electric lamp. It has been 

 mentioned elsewhere that both Dina microstoma and Glossiphonia 

 stagnalis are nocturnal in habit. When allowed a stone in the 

 aquarium for a hiding place, these leeches are content to remain 

 underneath it during the daj'. 



