SECT. 2] 



AND WEIGHT 



535 



As regards echinoderm embryos, we have the following table of 

 Vernon : 



Length °/^ change from white length 



Semi-darkness 

 Complete darkness 



Blue 



Green 



Red 



Yellow 



Driesch stated that these colours had no effect on Echinus embryos. 

 Here the favourable action of violet or blue and the unfavourable 

 action of green are not apparent. Nor in the case of trout fry could 

 Schondorff find any differences between the colours. The hatching 

 time of various eggs, however, according to Yung, does bring it out 

 again, as Table 75 shows, and the qualitative experiments of Schenk 

 on Rana and Bufo eggs and Fatigati on other material (infusoria) 

 demonstrate the same relation. 



Yung's figures: 



Table 75. 



Hatching time in days 



Violet Blue 



Loligo vulgaris 

 Salmo trutta ... 

 Limnaea stagnalis 



50 

 32 

 17 



53 

 35 

 19 



Yellow 

 58 

 34 

 25 



Red 

 58 



36 



Green 

 Dead 



36 

 Dead 



White 

 Dead 



35 



27 



In 1 91 3 Grein subjected the eggs of Gadus virens to light which 

 had passed through the following screens : 



Wave-length allowed to pass 

 A Red ... 610-710 /x/Li 



B Red ... 600-720 



C Red ... 600-700 



D Green ... 440-460 



E Blue ... All save light green 



and dark yellow 



Hatching times were quicker under D than under A, B or C, and 

 quicker under A, B or C than under E. 



Supino's results, expressed in percentage of embryos hatched after 

 a fixed period, were as follows : 



It may, on the whole, be concluded that the wave-lengths con- 

 tained in diffuse daylight which affect embryonic development are 



