MODIFICATION OF THE BEHAVIOR OF LAND ANIMALS 33 



The toads gave the same reaction to similar conditions. They 

 tested the region of high evaporation repeatedly during the 

 first ten minutes and then began to turn back and make short 

 stays in that section. The control is a little less symmetrical 

 than in most cases; for a more symmetrical control, see A, 

 Chart IV, Expt. 42. Both species show a preference for low 

 evaporation at the end of the period of experimentation. Chart 

 II, Expt. 75, shows rapid modification of the behavior of the 

 millipeds. (Fontaria). In the experiment, definite turnings began 

 at the end of nine minutes, when each animal had entered the 

 section of high evaporation. The control is a characteristic 

 symmetrical graph for the species. 



The graph of the spiders (Geolycosa) is difficult to interpret 

 and is peculiar, due to the fact that the spiders are very quick 

 and pugnacious, so that it is hardly possible for three of them 

 to be in the same third of the cage at the same time. Still, even 

 this graph appears to indicate what is true of single individuals 

 namely, an avoidance of the moist and medium air. This avoid- 

 ance does not begin until the end of eight minutes. The control 

 is typical of the species and shows fairly symmetrical distribution 

 of the spiders. 



Chart III shows the reaction of the wood frog to gradients of 

 evaporating power produced in three different ways. The graph 

 of Experiments 60 and 70 shows the type which results from 

 acceleration of movement or of movement due to mere stimulation. 

 In Experiment 60, one of the frogs was placed in each third. 

 Their commonest reaction to evaporation is to crouch close to 

 the substratum. If, however, the evaporation continues, they 

 finally hop, apparently at random. In the case of two of the 

 frogs in Expt. 60, the hopping was in the direction of the lowest 

 rate of evaporation where the frogs remained for an hour or more 

 after the observations here graphed were ended. Experiment 70. 

 shows first the stimulation of one frog leading to a series of hops 

 in the direction of lower evaporating power, of another frog a 

 little later in the direction of higher evaporating power which 

 in turn led to stimulation, resulting in hops in the opposite 

 direction. These graphs do not indicate modification. When 

 compared with the next graph, where temperature was used to 

 increase evaporating power, we note a striking difference (com- 

 pare the graphs of Expts. 60 and 70 on the one hand and 73), 



