THE SENSES AND THEIIl OKGANS. 



293 



tlio inoveiiR'nt was not so docidod. At iiii^lit llir diicctiuu was reversed, 

 ami tlie migration set toward tlie lilnary lii;iits, and tlic eoluny settled as 

 near tlieni as jjossible. 



This l)eliavior was so often and unilV>rndy observed that the conclu- 

 sion was ijuite satisfactory, liut I nevertheless made a series of experi- 

 ments which fully confirmed it. For exanii)le, one evening I found the 

 lirood massed at two points (a and b. Fig. 287) on either side of a toy 

 wooden cohniiu, hanging in a dim light which fell from a lamj) that 

 previously had been turned down. An oil lamp giving a Ijright light 

 was now lit, and so placed (beyond the j)oint c) that one cluster (at a) 

 was in shadow, tlie otlier (at b) faintly illuminated. In twenty minutes 

 twelve individuals had passed over from the jiartly shaded spot (b) to 

 the illuminated point (c), and about half the grouj) in the shadow (at a) 





Fig. 287. Experimeut to show the perception of light by young spiders. The group in shade were all 

 transferred to the shelf by lighting the lamp thereon. 



had crossed to the better light at b. The lamp was then removed to 

 the opposite side of the table, reversing the conditions of light, casting c 

 ill the shadow, b partly in the shade, and throwing full light upon a. 

 Instantly a movement began among the spiders now in the dark at c, 

 who turned and ran rapidly along the lines communicating with the col- 

 umn. In less than two minutes only four of the twelve remained ; one of 

 these soon followed, and shortly the other three. In the meanwhile the 

 shaded group at b was being broken up by an active transfer to the illu- 

 minated section at a. 



Another experiment gave the following results : I captured a female 

 Epeira sclopetaria at Atlantic City and placed her within a box to cocoon. 

 May 2(jth, a cocoon was formed in the angle of the .box, over which was 

 placed a triangular piece of sheeted spinningwork attached at the three 



