REACTIONS OF CERTAIN MOIST FOREST MAMMALS. 



would not run over the smooth tin bottom. After the rate of 

 evaporating power was determined the mice were put in the 

 cage, and tracings to the minute and second scale were made for 

 thirty-minute intervals. 



A control experiment was made after each experiment so that a 

 comparison could be made in the two cases. An animal might 

 spend as much time in one division of the control cage as it did 

 in the experimental cage but as the graph shows the movements 

 are of a different character. There is no direct orientation in the 

 control cage, and the mice wander back and forth through the 

 different divisions, and seem to be as well satisfied in one division 

 as the other. After one experiment was completed and the mouse 

 had selected the division of the cage which seemed to agree with 

 its physiological make-up, the different gradients were sometimes 

 reversed. The mouse always moved out and sought the condi- 

 tions it had formerly selected. 



3. Material. 



Only one species was used in the following experiments, the 

 white-footed wood mouse, Peromyscus leucopsus noveboracensis. 

 The experiments were made as soon as possible after the mice 

 were brought into the laboratory, and until experiments were 

 made they were kept under conditions as similar to those of their 

 natural environment as was possible. 



4. Experimental Results. 



(a) Reaction Experiments. The air was passed through sul- 

 phuric acid filters. 1 The amount of moisture in the air after 

 treatment depended upon the rate of flow, the temperature, the 

 original humidity of the air and the condition of the filters. 

 These filters became weaker from time to time due to the water 

 removed from the air. Ten-minute exposures were made of the 

 atmometers, as this time was sufficient to calculate readable 

 results. The rates are higher than they were in the experiments 

 of Shelf oid ('13) as the flows were greater and the same atmom- 

 eter containers were read. The evaporating results do not repre- 

 sent the rate in the cages for the cases were larger. 

 BULL., No. 25, '13. 



