HYDROTROPISMS OF FRESH-WATER INVERTEBRATES. 47 



results obtained from the experiments were; 32.3 per cent, 

 inward the water, 12 per cent, toward the sun, and 27 per cent. 

 inward the direction the head originally pointed. The per cent 

 of movements toward the water is too low to warrant the assump- 

 tii.n that the movements of the group, as a whole, have been 

 influenced by the water; however, certain individuals exhibit a 

 marked tendency to move toward the water. One individual 

 made 87 per cent, of movements toward the water; five, between 

 50 and 60 per cent.; three, between 40 and 50 per cent. Thus 

 nine individuals, practically half of the individuals used in the 

 experiments exhibited a tendency to move toward the water. 



Bright ne did not influence the movements. There was a 

 -li-Jn tendency to move in the direction the head was originally 

 pointed. 



When these beetles were given their freedom, some flew and 

 others did not. Of those that flew, more than 90 per cent, flew 

 to the water. 



SMM.I. |)i\i\<; BKKTLE (Laccophilns sp.?). 

 To test their fitness for work on the checkerboard plate, a few 

 experiments were conducted with a small diving beetle. On 

 account of its proneness to fly it is a difficult subject with which 

 to work; but, where one has sufficent patience it may be used. 

 It might be a good idea to clip its second pair of wings. On 

 escaping they always flew toward the water. 



THE I.AR<;K WATER STRIDER (Gem's renrigis Sa I'I.ATE \ I 



In working with the checkerboard plate, 27 indi\ iduals were 

 induced to perform 534 experiments. Seventeen individuals 

 were used near the stream where they were captured: tin- re- 

 mainder were taken to the shore of a lake. In nn>-t cases tin- 

 board was placed from five to ten feet fn-in tin- \\ater. In a few 

 cases it was necessary to place it nu-nty feet away. The results 

 are recorded in Table \ 1 1. 



In an infinite series of experiment-, if the factor- considered, 

 have no directive influence on tin- animal-, then J5 per cent, of 

 the movements should be toward the water. u.,s per cent, to- 

 ward the sun and 12.5 per cent, toward the origin. il po-iiion of 

 the head. The experiment- yielded 34.7 per cent, of movements 



