Adjustment of colour in various pupa^, etc. 410 



was similarly divided into 10 bays by partitions Avhicli 

 alternated with those of the roof. These were 0*0 cm. 

 high and their lower borders 2*0 cm. from the floor, while 

 they projected o 5 cm. from the back towards the glass 

 front. The object of this division of the internal surface 

 was to separate the larvae as much as possible, and thus 

 minimise their influence upon each other during the 

 sensitive period. The whole internal surface, except the 

 floor, of the box, and both surfaces of all the partitions 

 were lined with a chess-board pattern of orange and 

 black each 1'4 cm. square, and thus as nearly as possible 

 half the length of an average mature larvaa of P. hrassica.'. 

 when resting in Stage II preparatory to pupation. The 

 pattern was made by ruling the outlines of the squares in 

 pencil upon a sheet of deep orange surface paper and then 

 carefully pasting black tissue-paper squares over alternate 

 orange squares. 



It is much to be regretted that an experiment conducted 

 with so much care should have produced such limited 

 results as regards the numbers of pupae. 



The first box only contained 3 pupse which could be tabu- 

 lated wnth certainty on May 6th when the examination was 

 made. All were fixed in the left-hand bay of the roof, 

 near to the glass window. 



One pupa was fixed diagonally across a black square 

 with the end of its tail lying on another one, and the head, 

 directed towards the light, overhanging an orange square. 

 It was dead but had clearly been a (2) or a (3). 



The second was fixed parallel with the glass, the posterior 

 f of its body on the anterior part of a black square, but a 

 little overhanging an orange square in front, and the 

 anterior | similarly on orange and overhanging black as 

 well as orange in front (viz. towards light). It was a 

 greenish (1 j8). 



The third pupa was also parallel with the glass, although 

 the tail curved towards it. The posterior | of its body 

 was on the posterior (viz. away fiom glass) border of (so 

 that the right side overhung) a black square, the anterior 

 \ similarly on and similarly overhung orange. The left 

 side (away from glass) overhung the opposite colours in 

 each case except the posterior \ which curved towards 

 light, viz. towards the middle of the black square, so as to 

 overhang black. The pupa was a greenish (1 y). 



There were also two other dead pupae which could be 



