774 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



for each side. The degree of correlation between the numbers on the 

 two sides of the body is very small. This means that the right and left 

 legs are to a great extent independently variable in number of teeth, 

 which would lead one to suppose the variability dependent largely upon 

 local conditions within the pupa. 



Influence of Light of Different Colors. 



(a) Influence on fertility. For about ten weeks flies were allowed 

 to breed in chambers so constructed that the only light admitted passed 

 through colored solutions contained in flattened glass vessels. These 

 colors were red, blue, and green. An orange chamber was also in use, 

 but its culture died out after about six weeks. In addition, flies were 

 bred in white light and in darkness. 



Below are given the numbers of imagoes which had appeared in the 

 cultures at the end of the ten weeks : 



These numbers are of doubtful significance because of several unknown 

 factors entering into the result, such as differences in vigor among the 

 progenitors of the various cultures, possible differences in quality of food, 

 etc. The experiment should be several times repeated before conclusions 

 are drawn. 



(6) Influence on phototropic responses of larvae. The older larvae 

 were observed to be negatively phototropic in their responses to ordinary 

 daylight. In seeking situations for pupation they were found to have 

 distributed themselves as follows in the rectangular glass vessels in which 

 they were contained in the various chambers. The distribution was deter- 

 mined by the position of the pupa cases. 



