92 VICTOR E. SHELFORD. 



belonging to the anurans. In a few experiments with Chrophilus 

 nigritus, it was found that this frog possesses a similar set of 

 reflexes. 



The ground beetles (Pterostichus adoxus (i) and pennsylvanicus 

 (2) were very sensitive to the dry air, P. pennsylvanicus par- 

 ticularly so (Expt. 14, Chart V., p. 97). Here two specimens 

 of pennsylvanicus tried the dry air a few times and then began 

 to hesitate and turn back. The individual of adoxus was less 

 active but after one trial of the driest air and one turning from 

 the medium, came to rest in the moist air as did the pennsylvanicus 

 after a number of trials and turnings and at the end of fifteen 

 minutes. The loss of the stock of pennsylvanicus necessitated 

 the repetition of the experiment with adoxns alone. In the 

 second trial, the beetles when put in the center dashed lengthwise 

 of the cage once and by chance all bunched together in the driest 

 air, due to thigmotaxis and gregarious tendencies. Soon they 

 became very much stimulated and single individuals dashed to 

 the moist end of the cage and back with great speed. This 

 bunching interfered with the reaction and at the end of the 20- 

 minute period only two had worked out a preference for the 

 moist air. 



Fontaria was clearly stimulated by the dry air after less than 

 five minutes exposure in the observation tubes. The individuals 

 in the medium air showed less activity than those in the driest. 

 Individuals in the moist air remained quiet most of the time. 

 In most cases in the gradients (Chart III., Expt. 56, p. 91) the 

 Fontarias entered the driest air a number of times and then 

 began to show greater activity in the dry end, to stay a 

 shorter time there, to hesitate upon entering, and to turn back 

 occasionally. Their reaction to the dry air was clearly negative 

 as shown by a time preference for the moistest air, and the 

 haltings and turnings even, though the ability to orient in the 

 gradient seems poorly developed. 



Snails and slugs are not good for gradient experiments of short 

 duration because of their sluggishness. The slug (Philomycus 

 carolinensis Bosc.) was usually inactive in the moist air but quite 

 active during the first half hour in the dry air. Here the ten- 

 tacles were withdrawn in less than five minutes and remained so 



