248 Experiments upon the colour-relation, cc. 
Having been informed by my friend Mr. Poulton of the 
results of his observations, I suggested to Mr. Griffiths 
that he might conduct analogous experiments upon the 
larve in his possession, so that the results of two 
independent observations might be compared. Mr. 
Griffiths acted upon this suggestion, and conducted the 
series of experiments here detailed. 
Mr. Griffiths ultimately forwarded all his notes, 
together with the entire batch of pup obtained (between 
80 and 90 in number), carefully separated and labelled 
according to the various experiments, requesting me to 
classify the results, and to draw what conclusion I could 
from them. ‘Though I desired the treatment, as well as 
the experiments, to be Mr. Griffiths’s own work, he was 
so decidedly unwilling to undertake it that it only 
remained for me to agree to his request, and deal with 
his material to the best of my ability, upon the lines 
laid down in Mr. Poulton’s paper. 
To this explanation of my position in the matter I 
can happily add that I have been greatly assisted by 
Mr. Poulton, who was so good as to assist Mr. Griffiths 
and myself in drawing up the primary classification of 
the pup, according to the colour-standards he had 
originated. 
Notwithstanding the subsequent assistance given by 
Mr. Poulton, the experiments themselves were, of course, 
entirely independent, and the conditions were somewhat 
varied; but Mr. Griffiths agrees with me in feeling 
confident that the results are brought into a perfectly 
true and safe comparison with those obtained by Mr. 
Poulton in his original experiments. 
It is unnecessary to refer here to the literature of the 
subject, for an account of earlier observations is given 
in Mr. Poulton’s previously-quoted paper. There is, 
however, a remark of Prof. Meldola’s, which is so im- 
portant that I must quote it at length. The following 
words were used by Prof. Meldola on the occasion of the 
reading of a paper by Mrs. Barber in 1874 before this. 
Society* :—‘‘ The action of light upon the sensitive skin 
of a pupa,” he said, ‘‘had no analogy with its action on 
* This paper, which was communicated by Mr. Darwin, bore 
chiefly upon the pupx of Papilio nireus of Cape Colony (Trans. 
Ent. Soc. Lond., 1874, p. 519). 
