On the Transmission of Environmental Effects. 115 



discrimination, so that the two appear exactly alike, although by another 

 kind of light a difference is plainly visible. 



8. Colour adaptation increases the perception of relative difference for 

 colours other than the dominant. 



9. The conscious judgment has very little effect in colour adaptation. 



10. Colour adaptation greatly helps in the correct discrimination of colours 

 and masks the effects of the very great physical differences which are found 

 in different kinds of illumination. 



11. Spectral yellow, after colour adaptation to green, still appears yellow, 

 and not red. 



12. Colour adaptation appears to produce its effects by subtraction of the 

 dominant colour sensation, and not by directly increasing the complementary. 

 Spectral blue does not appear brighter after colour adaptation to yellow. 



The Transmission of Environmental Effects from Parent to 

 Offspring in Simocephalus vetulus. 

 By W. E. Agar, Glasgow University. 



(Communicated by Prof. J. Graham Kerr, F.R.S. Received October 15, 1912, — 



Read January 23, 1913.) 



(Abstract.) « 



In a common daphnid, Simocephalus vetulus, the effects of environment (in 

 its widest sense) on one generation may persist on generations removed from 

 that environment, the phenomenon being clearly a case of "parallel induc- 

 tion " (Detto). Three main experiments were carried out, in addition to 

 a number of experiments on related problems in the biology of the animal. 



Experiment A. — The character dealt with was the ratio between the total 

 length of the new-born individual and the width between the ventral edges 

 of the valves of the carapace. When the animals are fed with certain 

 protophyte cultures, the valves become rolled back in a curious way, so that 

 in transverse section the animal is bell-shaped instead of oval, and the body 

 appendages, instead of being nearly concealed by the carapace, are fully 

 exposed. The distance between the edges of the valves is enormously 

 increased, and thus the ratio length/intervalvular width correspondingly 

 decreased. 



Experiment B. — The character dealt with was the length of the new-born 



