414 



THE AMERICAN NATURALIST [Vol. LIII 



tight, I should have been inclined to explain such a meas- 

 ure of promptness in moving to the water as due, perhaps, 

 to the effect of moisture from the stream. 



Of course if the means of finding the brook was 

 mainly through vision, it was to be expected that the 

 gerrids would be a little less prompt in reaching the 

 water, because less reflection from the surface of the 

 brook could be seen than was true with the barrier re- 

 moved. Unfortunately the movements of the leaves by 

 the wind permitted many bright reflections to pass 

 through the barrier. Lying flat on the ground, with my 

 eyes as close to it as i)racticable, in order to take a posi- 

 tion as nearly the same as possible to that of the water- 

 striders, I found that I was still able to see the bright 

 sunlight of the hot summer day, reflected from the sur- 

 face of the water. I planned to use another form of 

 barrier and test this matter fully, when, because of the 

 character of the season, I was compelled to take up cer- 

 tain other observations, and I have not yet had the oppor- 

 tunity to sui^plement this work with additional experi- 

 ments. 



