VERMES, FLY LARVAE, AND ECHINODERMS 179 



" When the diffuse daylight which struck the [fly] larvae 

 came from two windows the planes of which were at an 

 angle of 90° with each other, the paths taken by the larvae 



Fig. 28. Direction of movement of fly larvae in light from two sources; n, m, 

 direction of rays; i, course in light from n and m 50 and 5.5 ca. m. respectively; 

 2, course in light from n and m, 50 and 15 ca. m. respectively; 3, course in light 

 from n and m, 50 and 60 ca. m. respectively. Lines i, 2, and 3 represent the aver- 

 age direction of several courses taken by each of three larvae, 



lay diagonally between the two planes; " and (p. 2), " It is 

 explicitly stated in this and the following papers that if 

 there are several sources of light of unequal intensity, the 

 light with the strongest intensity determines the orientation 



