96 EXTERNAL FACTORS III. 4 



more harmful than red, while green exerts about the same effect 

 as blue (copper sulphate). The author states, however, that in 

 two other experiments the larvae were entirely killed off by 

 the green light though developing perfectly in the white. He 

 also adds that in violet light no development was possible owing 

 to the swarms of bacteria. 



TABLE XII 



Percentage change of size. 

 Semi-darkness +2-5 



Absolute darkness . 



Blue (copper sulphate) 



Green 



Red ... 



Blue (bleu de Lyon) 



-1-3* 



-4-5 



-4-8 



-6-9 



-74 



Yellow -8-9 



* Almost within the limits of experimental error. 



In the Pluteus Vernon found that both the oral and the 

 aboral arm-length decreased in darkness, green and blue (bleu 

 de Lyon) lights, while blue (copper sulphate), yellow, and red 

 light exerted little influence on this magnitude. 



It only remains to be added here that Blanc and Fere have 

 brought forward some not very satisfactory evidence to show 

 that white light is favourable to the development of the Chick. 

 Fe're' has also stated that red and orange lights are more 

 harmful than white, while violet has about the same effect. 

 The experiments are, however, vitiated by the fact that the 

 eggs were not turned over. 



LITERATURE 



L. BLANC. Note sur 1'influence de la lumiere sur I'onentation de 

 1'embryon dans I'oauf de poule, C. R. Soc. Biol. (9) iv, 1892. 



L. BLANC. Note sur les effets teratogeniques de la lumiere blanche 

 sur Pceuf de poule, C. B. Soc. Biol. (9) iv, 1892. 



H. DRIESCH. Entwicklungsmechanische Studien II, Zeitschr. wiss. 

 Zool. liii, 1892. 



C. FEKE. Note sur 1'influence de la lumiere blanche et de la lumiere 

 coloree sur 1'incubation des ceufs de poule. C. R. Soc. Biol. (9) v, 1893. 



T. LIST. Ueber den Einfluss des Lichtes auf die Ablagerung von 

 Pigment, Arch. Ent. Mech. viii, 1899. 



J. LOEB. A contribution to the physiology of coloration in animals, 

 Jonrn. Morph. viii, 1893. 



J. LOEB. Ueber den Einfluss des Lichtes auf die Organbildung bei 

 Thieren, Pfluger's Arch. Ixiii, 1896. 



