476 Mr. 'P o\x\ion' s further experimenU upon 



green against orange backgrounds. And yet Mr. Bateson 

 admits such an "attempt" on the part of betularia {I.e.; 

 p. 212). 



Mr. Bateson fails to apprehend that if the pupae had 

 resembled the various artificial backgrounds, it would 

 have been the strongest blow against the theory of the 

 protective significance of the change. We can hardly 

 imagine the jiroduction, under the theory of natural 

 selection, of adaptation to surroundings which had never 

 before been met with in the life of the species, and it 

 would be clear that we had to deal with some other 

 power. I have no prejudice against my own discoveries 

 that I should seek to minimise them ; but the chief 

 reason why I have failed to see in them what some 

 others have believed they have seen, viz., the indications 

 of some new power in the moulding of species, is because 

 I have only been able to produce those changes which 

 can be produced by a natural environment. Even the 

 golden pupae of V. iirticce form no exception ; for healtby 

 individuals are known to occur, although rarely, upon 

 the leaves of nettles.* 



Mr. Bateson does not seem to see that his opinion 

 that the golden form is conspicuous is really at variance 

 with his contention that the pupal susceptibility does 

 not tend towards concealment ; for, in nature, the sus- 

 ceptibility is chiefly employed in checking the production 

 of this very form. Until my experiments, the golden 

 pupae were little known, except when diseased. 



We have seen that the colour-changes of all species 

 proved to be susceptible certainly tend towards con- 

 cealment, V. urticcB being alone disputed ; that the 

 protective green and dark forms of V. io certainly 

 correspond physiologically to the gilded and dark forms 

 of V. urticce, while the dark forms of the latter are 

 certainly protective; for the pupa would be dark on a 



'■'■' Mr. Merrifield tells me that, during the last week of August, 

 1892, he found about 50 pupse of V. urticcB, evidently belonging to 

 one company, suspended to the stalks of nettles, or sometimes of 

 other plants growing with them. All were entirely golden, and all 

 produced ichneumons. A few days later Mr. Merrifield found a 

 colony of over 200 nearly mature larva:>, and among them about a 

 dozen pupas also on the nettle-stalks. Tliese were equally golden, 

 and about half produced imagos.the remainder being ichneumoued 

 (one died from some unknown cause). See also Experiment 63, 

 p. 382, 



