HVDROTROPISMS OF FRESH-WATER INVERTEBRATES. 



45 



of each pair were painted with a thick coat of lampblack mixed in 

 liquid glue. The eyes of the other were normal. Twelve pairs 

 were used. They were placed fifteen feet from the water. In 

 ten cases the one with good eyes reached the water in a short 

 time and the one with blinded eyes failed to do so. In one case 

 neither reached the water. In another the one with blinded 

 eyes reached the water and the one with good eyes wandered 

 iv from the water. The experiment with this last couple was 

 repeated and yielded similar results. 1 It is probable that the 

 eyes of this blinded crayfish were not entirely blind; because, on 

 tin- next day, after the eyes had been repainted, this individual 

 behaved like the other blinded ones. Its companion of the first 

 day died over night; hence, it was not possible to re-test it. 



The-e experiments with blinded crayfish, when considered in 

 connection with the experiments with normal crayfish, demon- 

 strate that the stimulus by means of which a body of water 

 controls the movements of the crayfish reach the animal through 

 the eyes. 



GIANT WATER BUG [Belostoma (Zaitha) fluminea] (PLATE IV). 



The exceptionally dry summer caused many ponds to go dry 

 and it was impossible to secure enough specimens to conduct an 

 extensive number of experiments. Five individuals were used 

 and 109 experiments performed. The checkerboard plate was 

 placed ten feet from the water. The results of these experiments 



are recorded in Table Y. 



TABLE Y. 



GIANT WATER BUGS [Relo^ioma ('/. 



1 In tl, i- tw.-i 



one pair while 1 \vatrhcd thr "tl 



w. i a tinn.-; my wife watching 



