420 Mr. F oulton s J'urtlier experiments upon 



This table proves, so far as is possible with so limited 

 a number of individuals, that the sensitive period, during 

 which the pupal colours are determined, is later in this 

 species than in V. urticce. Similar transference experi- 

 ments (Trans. Roy. Soc, I. c, p. 360) in the case of this 

 latter species proved that Stage II. is the most sensitive 

 part of the period before pupation. This table shows 

 that in T^ io Stage III. is probably far more important 

 in this respect. In fact the results obtained, when this 

 stage and the end of 11. alone were passed through in 

 certain conditions, were practically uniform with those 

 witnessed when the larvae were exposed to the same 

 conditions for all three stages. There is one marked 

 exception in the case of the dark pupa formed in white 

 surroundings. The larvae which were transferred into 

 darkness formed even darker pupae than those which 

 were exposed throughout to this condition. 



This high sensitiveness, during Stage III., har- 

 monizes very well with the results obtained from 

 Experiments 77 — 92, which showed that the stage is of 

 extreme relative length in this species. In writing 

 this paper from the notes taken at the time, as soon as I 

 found the great difference between this species and 

 V. urticfe in the relative lengths of the stages, I antici- 

 pated that the transference experiments would, when 

 tabulated, lead to the conclusion indicated above. It is 

 probable that the great length of Stage III. has caused 

 the point of greatest susceptibility to be shifted into it. 

 It has been shown {I. c.) that this period is somewhat 

 sensitive, probnbly in its earliest part, even in V. urticce. 

 It is likely that the great extension of this earliest sen- 

 sitive period accounts for, at any rate, the chief part of 

 the difference between the lengths of Stage III. in these 

 two species of Vanessa. 



The results are also interesting in confirming the 

 previously described effects of the various environments 

 made use of, and in showing the influence of darkness. 



Coijlictiiig Colour Experiments. Experiments 101 — 103. 



1892. 



I was most anxious to repeat the experiments already 

 described in the case of I', urticce (see pp. 391 — 397), and 

 thus, from the behaviour of this most sensitive species, to 



