114 A - - WEESE. 



The figures accompanied by letters at the top of each section of the chart desig- 

 nate the number of the experiment. Experiments designated by the same number 

 and consecutive letters were performed with the same animal and consecutively. 

 Otherwise the experiment numbers are entirely arbitrary. The upper line of 

 three figures in each section e. g., 34, 19, 4, in ia, indicates the relative humidity 

 of the air passing through the corresponding thirds of the cage, as computed from 

 standard wet and dry bulb thermometer readings. S S S in ic and $c indicates 

 that in these control experiments the air was still and the same in all sections of the 

 cage. The lower line of figures, e. g., .5, .9, 1.5 in ia, represents the standard at- 

 mometer reading, for a similar twenty-minute period, of the air passing through the 

 corresponding third of the cage. Thus, in Experiment la, the relative humidity of 

 the air passing through the left-hand third of the cage was 34 per cent., and the 

 corresponding atmometer reading .5 c.c. In the middle third the relative humidity 

 was 19 per cent, and the atmometer reading .9 c.c., while in the right-hand third the 

 relative humidity was 4 per cent, and the atmometer reading correspondingly high, 

 or 1.5 c.c. The rate at which the air passed across the cage was in each case 25 

 liters per sec. 



Where the record is in the form of a dotted line, it indicates that the animal, 

 in the corresponding period, either attempted to escape from the cage or to burrow 

 in the sand on the cage bottom. In the records of experiments 3 and 40 the circles 

 and the parallel lines following indicate that the animal burrowed under the sand 

 and remained covered for the period indicated. In the record of experiment 5a 

 the circle indicates that the animal was under the surface of the sand for a brief 

 time only. For discussion of individual experiments see text. 



Experiments ia, ib, Control, ic. (Chart I). The tracing which is the graphic 

 record of experiment ia shows that the animal, for the first minute and a half, re- 

 mained in the two portions of the cage where evaporation was lowest, then, at 

 intervals about one minute made brief visits to the drier section. Following the 

 fifth minute there is recorded a stay of over one minute in the driest third of the 

 cage. Aside from this all the longer rest periods were spent in the opposite end of 

 the cage. It will be noticed that, in general, the apices of the curves at the right 

 are sharper than those at the left, indicating quicker turning in this region. In the 

 first minute the animal turns away from the drier portion of the cage twice, once 

 in the fifth minute, again in the eighth, tenth, sixteenth, eighteenth and twentieth 

 minutes. There is only one turning back from the more moist regions, in the 

 nineteenth minute. 



The record of ib is of almost the same character, with more avoidance of the 

 dry end, as there are ten turnings during this twenty-minute period. 



The control, ic, in which the same animal was used shows somewhat greater 

 activity than the two previous experiments, as the line crosses the area representing 

 the cage a greater number of times. This curve, however, is not in the least one- 

 sided, showing that the animal avoided no region of the cage. As indicated at the 

 top of the chart, there was no air current through the cage in the control. 



Experiments 20, 2b. In this experiment one end of the cage was supplied with 

 air nearly "saturated " with moisture, as is indicated by the relative humidity of 98 

 per cent, and an atmometer reading of .2 c.c. During the first twenty-minute 

 period, represented by tracing 2a the animal spent a littlemoie time in the dry end 

 than in the very moist region. During the second twenty-minute period (26) the 

 animal reached the dry third but six times, turning back almost immediately in 



