518 



S. O. MAST 



tion in the white beam of light was adjusted until the animal in 

 each case followed this line. To accomplish this it was often 

 necessary to make them travel across the field several times for 

 each color tested. This was done by letting them crawl onto a 

 piece of tin of the proper size at the end of the course and then 

 gently transferring them to the beginning and letting them crawl 

 off again. 



The specimens^ used in the observations on Lumbricus were 

 very small, averaging only about 4 cm. in length. All of them 

 were found in a small area on a sidewalk after a heavy rain- 

 storm (September 26) . After reaching the laboratory they were 

 kept continuously in darkness until used in the observations, all 

 of which were made the following day. The results obtained in 

 these observations are presented in table 13. The averages of 

 these results corrected for unequal distribution of energy in 

 the spectrum are presented in the last column of this table. 



TABLE 13 

 Lumbricus terrestris. Relation between wave-length and stimulation 



For description of table see legend table 2, p. 492. 



3 Some of these specimens preserved in formalin were examined by Prof. 

 Frank Smith and identified as very young Lmnbricus terrestris. I am greatly 

 indebted to Professor Smith for his efficient service. 



