2/8 'Journal of Comparative Neiirologv and Psychology. 



intensity of light within the dark box below the degree used in the 

 case of the black screens. The results of the series of experi- 

 ments with white screens may be summarized as follows: 



Case i^ — When the larva was oriented with back above and 

 the screen, held vertically, was so introduced from before that its 

 plane was at right angles to the longitudinal axis, and parallel to 

 any transverse axis of the larva, there resulted a rotation through 

 i8o° with, perhaps, a fall to the bottom. After this, and as 

 a result of a revolution on the body-axis, a "righting reaction" 

 usually occurred and the back would again be brought above. 

 Now, with the head directed away from the white screen, the larva 

 might either approach or depart from it, according as the pro- 

 gressive orientation was positive or negative. Sometimes, instead 

 of producing a rotation through an arc of i8o°, the larva under- 

 went a series of rotations, its body forming a constant part 

 of the circumference. The final orientation mentioned above 

 would, however, invariably succeed. In case the screen was not 

 held squarely before the larva, but somewhat at an angle to any 

 transverse axis, the consequent reaction was a direct side swing 

 away from the screen in order to place the longitudinal body-axis 

 perpendicular to, and the head aw^ay from, the screen. In other 

 cases there resulted a combination of the side swing and the for- 

 ward rotation, so that the larva performed a sort of "half-somer- 

 sault," and eventually assumed the normal swimming position, 

 with the head directed away from the screen, as pointed out above. 



Case ij — When the larva was oriented with the back above and 

 the screen, held vertically, was made to approach the posterior 

 end of the larva, no change in the body-orientation resulted. There 

 might occur, however, either a positive or a negative progressive 

 orientation. 



Case i6 — In this case the larvae were swimming promiscuously 

 about the container. When the screen was made to approach 

 larvae which held a position with the back above and one side turned 

 toward the screen, these larvae experienced a swing of their longi- 

 tudinal axis so that the head came to be directed away from the 

 screen and the longitudinal body-axis at right angles to the plane 

 of the screen. 



Case ly — When the screen, held horizontally, was made to 

 approach, from below, a larva which held the normal swimming 

 position, one of two reactions(which probably represent different 



