264 Experimental Zoology 
AvERAGE LENGTH LENGTH COMPARED WITH 
WuiteE Licut 
White 24.4 100 
Violet 28.5 117 
Blue 25.6 105 
; Yellow 24.3 99 
Red 20.3 83 
Green 16.9 70 
Here also I question whether the results have any certain value 
because of the variability shown by tadpoles reared in dishes, and 
on account of the difficulty of keeping the other conditions the 
same. 
Vernon’s results with sea-urchin larve are more significant, 
because the growth, in this case, depends little, if at all, on the 
food supply. 
' LenctTu 
Semi-darkness tas 
Complete darkness ~1.3 
Blue (copper sulphate) —4.5 
Green — 48 
Blue (Lyons blue) — 7.4 
Red —6.9 
Yellow —8.9 
In violet light all the larvae died, owing to bacteria. The order 
of growth for the other colors was: white, blue (copper sul- 
phate), green, red, blue (Lyons blue), yellow. The order is so 
different from that given by Yung that, although done on 
different animals, the interpretation of the real influence of the 
light is probably open to question. 
Beclard found that the eggs of the fly, Musca carnivora, 
when reared under different colors developed fastest in violet 
light and most slowly in green. The sequence for all the colors 
used is violet, blue, red, yellow, green. This order agrees more 
