SPECTRAL COLOR AND STIMULATION 519 



These results indicate that the distribution in the spectrum of 

 stimulating efficiency for LumbricuB is essentially the same as it is 

 in the Arenicola larvae, Euglena, Phacus, Trachelomonas and 

 Gonium (table 15). The location of the region of maximum 

 efficiency corresponds fairly well in all and the fact that the total 

 effective region is somewhat shorter for Lumbricus than for the 

 other forms is no doubt due to the difference in the illumination 

 used in the experiments, it being considerably lower in those on 

 Lumbricus than in those on the other forms. 



Allolobophora foetida was also tested but only a few times and 

 the responses were always rather indefinite, but the results ob- 

 tained indicate that the relation between stimulation and wave- 

 length in this form is the same as it is in Lumbricus terrestris. 



Blowfly larvae 



The blowfly larvae used in the following work were obtained 

 by exposing pieces of raw beef. No attempt was made to iden- 

 tify them. They were kept continuously in very weak light or 

 in darkness and all individuals which did not orient fairly 

 accurately were discarded. 



A total of 12 series of tests was made (September 18 to 23) with 

 larvae in various stages of development. In the first four the 

 collimator slit was 1 mm. wide and the ocular slit 2.5 mm, 

 wide. In the next seven both slits were 1 mm. wide and in the 

 last both were 0.5 mm. wide. There was no marked difference in 

 the results obtained under these various illuminations. Taken 

 as a whole they were not very satisfactory and much more accu- 

 rate results could undoubtedly be obtained with the method 

 employed if more time were devoted to the work. 



The results show clearly, however, that the distribution of 

 stimulating efficiency is more nearly in harmony with that found 

 in Chlamydomonas than with that found in any of the other 

 forms studied. The results obtained in three of the most satis- 

 factory series of tests made are given in table 14 and the averages 

 of these three series, corrected for unequal distribution of energy, 

 are plotted in figure 4. These results indicate that the regions 

 of maximum stimulating effect and efficiency are respectively 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY. VOL. 22, NO. 3 



