1913] Gee: Behavior of Leeches 231 



numbers of the Dina would begin to crawl up the sides and 

 corners of the dish, squirming and twisting over one another. 

 The same result was secured in jars placed on a springy board 

 and jarred several times repeatedly. This tendency does not 

 persist for any great length of time ; for the animals release 

 their hold in a few minutes and either drop to the bottom of 

 the dish to crawl around or swim about as is their usual reaction 

 when in a fairly active condition. A second heavy jar or series 

 of jars produces nothing lil^e so marked an effect, the animal 

 apparently regaining its normal equilibrium rather quickly. 



When a half dozen specimens were placed in water of 36° C 

 they became exceedingly active. They would settle to the bottom 

 of the dish often, and, executing random movements, would either 

 move off rapidly by looping or giving the swimming response. 

 Even water cooled to several degrees lower gave no evidence of 

 the tendency to produce reversal of geotactic response. The 

 effect of the heat seemed to find expression in the increa.sed 

 activit.y of the individual, and the accompanying excess of random 

 movements. 



It is rather interesting that in two forms as widely separated 

 in habits as are the land leeches of Japan and the Dina of this 

 country, a purely aquatic form, there should be the same ten- 

 dencies of behavior in this regard, even though the tendency to 

 reversal is not nearly so pronounced in the nephelid as Whitman 

 has described it for the land form. 



The blood-leeches seem to show an indifferent geotactic re- 

 sponse when kept in aquaria. A dozen specimens kept under 

 observation for several months in the laboratory were noted to 

 lodge themselves out of the water almost as often as they remained 

 immersed in it. When out of the water they suspend themselves 

 by the two suckers, either stretching in a straight or curved 

 position along the sides of the dish, draping themselves in a not 

 ungraceful festoon from the under surface of the cover of the jar. 



9. Influence of He.vt 

 No attempt was made to determine the optimum temperature 

 conditions of the leeches. In Dina mierosioma temperatures as 

 low as 10° C, when continued for several hours lower deeidedlv 



