I JO DWIGHT ELMER MIXXICH. 



trials with oil. Great care had to be exercised in trials with oil, 

 not to allow the body to come in contact with the oil saturated 

 cotton and further, to remove the oil from the legs after each 

 trial with shreds of filter paper. Otherwise the oil spread over 

 the body and quickly killed the animal. With the proper pre- 

 cautions, however, flies could usually be given repeated trials 

 with oil and yet be kept in good condition. 



FIG. 2. Apparatus used in testing the effect of tarsal contact with water. The 

 apparatus consisted of a petri dish filled with water. Near the center are two 

 rectangular pans: a, containing a cotton pad saturated with distilled water, and 

 b, containing a cotton pad saturated with paraffin oil. 



The details of the first two sets of experiments were briefly 

 as follows. To the bottom of a glass petri dish 14 cm. in diam- 

 eter, two rectangular metal pans 2 cm. by 3.5 cm. by 1.5 cm. 

 deep were fastened with wax. The petri dish was filled with 

 distilled water nearly to the edge of the pans. In one pan (a, 

 Fig. 2) was placed a smooth pack of absorbent cotton saturated 

 with distilled water; in the other pan (b, Fig. 2) a similar pack, 

 saturated with paraffin oil. The animals were tried in three 

 positions: (i) with their feet in contact with the cotton of pan a, 

 where they were subjected to the contact stimulus of water, and, 

 the distance stimulus of water vapor; . (2) a similar position in 



