404 Mr. F. Merrifield and Mr. E. B. Poulton on 



seven green pupae (3 h) were formed as against five light 

 ones (3 a). The influence through glass (35, 36, 37) was 

 undiminished ; but that at a distance (34, 38) was im- 

 menselyreduced, a single intermediate pupse (2),a largenum- 

 ber of light (3 a), and only a few gree7i (3 &) being produced. 



Planed deal (39 — 41) seemed to produce effects com- 

 parable to those of white, viz. that form of pupa out of 

 the various possible degrees, which harmonized best with 

 the background, viz. light (3 «), a single intermediate one 

 (2) also appearing. No appreciable difference is to be 

 noted between the effects in strong light (39), shade (40) 

 and at a distance (41). 



Looking at these experiments as a whole, the much 

 smaller effect produced by the coloured backgrounds 

 upon the pupae " on the glass," viz. at a more or less 

 distance from the effective stimulus, harmonizes well with 

 the results of previous investigation. 



The strong tendency of the pupse, or rather the larvae, to 

 face the light directly is well shown in the results of 

 Experiments (6) and (35) where the positions are recorded. 

 The great majority of the exceptions were due to the larva 

 placing itself parallel and in close proximity to the clear 

 glass front. A similar tendency to seek the angles 

 between a horizontal and vertical surface probably in part 

 explains the fact that so high a proportion directly faced the 

 light, the body line having been drawn into parallelism and 

 often into contact with the sides. In these experiments 

 only one pupa was parallel with and close to the back, but I 

 have noticed very many pupa3 o^ Pieris hrassicx in shallower 

 breeding-cases, in this position. The few complete ex- 

 ceptions in (6) and (35) in which the head pointed directly 

 away from the light are enough to show that susceptibility 

 is unaffected by orientation. 



Mr. Merrifield is to be congratulated in having proved 

 the high degree of sensitiveness possessed by this pupa. 

 While the susceptibility is as great as that of any other 

 species, even of the highly sensitive Vanessa io, the range 

 of controllable modification is jjrobably wider than in any 

 other as yet investigated in sufficient numbers. This is 

 shown by the production not only of green and darh forms, 

 but of pale and grey pupae upon such backgrounds as 

 white paper and planed deal. At the same time the 

 range is not nearly so great as that of the larva of Amphi- 

 dasis hetularia, which can produce on appropriate dark 



