XXXIII 



had no effect. Of more significance are the observations by Pgui.ton who 

 certainly is a strong and by no means unbiassed supporter of the said theory 

 but whose experiments have been conducted on so large a scale and with so 

 much accuracy that, even when we are unable otherwise to accept his con- 

 clusions, the facts observed by him merit every confidence. Six pupae of 

 Vanessa Io L., which occur in two colours in nature — dark green and more 

 rarely yellowisch-green — reared by him in a surrounding of yellowisch-green 

 tissue paper were all of that colour. In the pupae of Argynnis Paphia L. 

 and Vanessa Polychloros L., according to Wood and others the environment 

 caused them to become darker or lighter but otherwise the colour was not 

 affected. In Pieris Brassicae L. and P. Rapae L. the pupae become a 

 beautiful smaragd-green from a yellow or orange surrounding but a black or 

 white environment induced only darker or lighter shades ; the former also resulted 

 from every other surrounding except yellow or orange; blue has no influence 

 on Pieris pupae nor has orange on those of Vanessa. The most important 

 results were obtained by Poulton in experiments on the pupae of Vanessa 

 Urticae L., which he was able to carry out on a large scale. The larvae 

 which were the subject of these experiments were placed in green surroundings 

 in the hope of producing green pupae which in this species do not occur in 

 nature; but in vain, the pupae were only "somewhat darker than usual and this 

 suggested a trial of black surroundings, from which the strongest effects were at 

 once witnessed ; the pupae were as a rule extremely dark with only the smallest 

 trace, and often no trace at all, of the golden spots which are so conspicuous 

 in the lighter forms. A not inconsiderable number, however, retained the 

 normal light colour with golden dots. These results suggested the use of 

 white surroundings. The colours of nearly 1 50 chrysalides obtained under such 

 conditions, were very surprising. Not only was the black colouring matter as 

 a rule absent, so that the pupae were light-coloured, but there was often an 

 immense development of the golden spots, so that in many cases the whole 

 surface of the pupae glittered with an apparent metallic lustre as if they were 

 covered with gold-leaf". Sometimes the pupae were light pink in colour. 

 Finally a golden surrounding was tried and the same effect secured as with 

 white but with a great increase in the number of golden pupae. Poulton, 

 moreover, observed that whereas an orange surrounding induces a dark smaragd- 

 green in pupae of Pieris, that colour does not influence Vanessa pupae and 

 also that blue has no effect on Pieris pupae. 



Concerning the pupae of Vanessa Io L., Dr. Kathariner {Bio/ogisckes 

 Centralblatt i8gg) has also published some observations in which, however, he 

 considers the rare green form a variety and the lighter or darker brownish-grey 



5 



