Experiments upon the colour-relation, &c. 251 
or suffered accident ; 5 died during the pupal ecdysis, 
but only one was attacked by parasites ;* 2 were dis- 
qualified for other reasons: thus 74 form the data upon 
which this paper is written. 
2. THE METHODS OF EXPERIMENTATION. — Such indi- 
viduals as were to be submitted to the influence of a 
single predominating colour were surrounded by the 
particular tint in the following manner :—The internal 
surface of the jar was first completely lined with tissue- 
paper of a selected colour, placed loosely (to allow of easy 
removal); the larva was then placed in it, together with 
a mignonette-leaf or two in every instance, a point which 
it is necessary to bear in mind; a square piece of the 
same paper, bearing the diary number of experiment, 
was next laid over the mouth of the jar, to complete 
the environment, and this was covered by a piece of 
clear glass to secure it and to admit a sufficient amount 
of light. 
The colours employed in the single-colour experiments 
were Black, Pink, Yellow, Green, and Blue. Tinfoil 
was also tried in two cases, but without producing any 
noteworthy results (only the average grey colour typical 
of “normal”? specimens), and hence these are not 
included in our classification. 
Most of the larve remained subjected to the various 
imposed influences for a period which covered several 
days; that is to say, throughout the ‘‘ Stages I. and III.” 
of Mr. Poulton (see below). Unfortunately, however, Mr. 
Griffiths did not take any notes as to the length of the 
periods during which the different larvee were respectively 
influenced. Mr. Poulton found it convenient to consider 
the period preparatory to pupation as consisting of the 
three following ‘‘ stages” :— 
“ Stage I., in which the larva quits its food-plant” in 
search of a suitable situation for pupation. 
** Since writing the above a dipterous parasite emerged from 
another specimen on January 31st, whilst no less than seventeen 
have emerged since the reading of the paper, nearly all at the time 
when the imagines would have matured. There was no evidence 
whatever of the presence of parasites, and that they had no 
influence in relation to the colour is clear from the fact that they 
occurred indiscriminately upon all grades of colour. In every 
case only one parasite was produced from each insect attacked. 
