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



and excepting Nos. 4 and 12). They were collected by 

 Miss Cora B. Sanders (St. Helens and Reading), by Mr. 

 W. Holland (Oxford), Mr. A. H. Hamm (Oxford), and by 

 myself (St. Helens). Experiments 13, 41, and 42 were 

 conducted by Miss Sanders; 5, 6, 37, 38, 89, and 40 by me, 

 and the remainder by Mr. Holland and Mr. Hamm. I 

 wish to express my warm thanks for all the large amount 

 of kind help I have received. 



The conditions of experiment are sufficiently shown in 

 the following tabular statement (see pp. 411 — 416), the con- 

 stitution of the reflected light being given in the Appendix. 



The pupae were examined on May 6, 7, 8, 9, 10 and 11, 

 1899, when several of them had emerged or were emerg- 

 ing. All these, however, are indicated below, and nearly 

 all could be tabulated with considerable accuracy. 



The positions of the pupae in relation to the receptacles 

 employed and to the light were noted in a large number of 

 examples, with the following results. Thirty-six pupae 

 were fixed to the roof (or in the angle between it and the 

 back), with a direction parallel with the front (generally 

 clear glass) and back ; 25 were fixed to the front, back, 

 or sides in a vertical position with the head uppermost 

 (including a few with the head downwards — cases in which 

 pupation certainly occurred during a temporary reversal of 

 the position of the receptacle) ; 41 were fixed, almost 

 invariably to the roof, with the head pointing directly 

 towards the light, viz. with the line of the body at right 

 angles to the front (generally clear glass); 11, otherwise 

 similarly placed to the last, had their heads pointing 

 directly away from the light; 15, otherwise similar, had 

 their heads obliquely directed towards the light; 10 their 

 heads obliquely directed away from it. It is therefore 

 clear that there is, upon the whole, a tendency to direct 

 the head towards the light, although the tendency is not 

 nearly so strongly marked as in P. najn. There was no 

 appreciable difference in the colour according as the head 

 pointed towards or away from the light. 



Reviewing the results of the tabulated experiments, 

 the effect of black (1 to 9) is, with certain exceptions, 

 similar to that which has been obtained before, and also to 

 Mr. Merrifield's investigations carried on simultaneously. 

 These exceptions are the very dark pupae obtained in 

 almost complete darkness (8), and the very unusual light- 

 ness of some of those in dim light (6, 7). 



