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my earlier observations in Java. During my stay in Java I did not indeed, 

 conduct actual investigations in this field, the importance whereof had not 

 attracted my attention at that time, but nevertheless I bred many larvae of 

 Papilio Memnon L. and P. Polixes L. for other purposes and my notes made 

 at the time are of value also in this connection. From these it appears that 

 in the pupae reared under varying conditions of light and darkness no influence 

 of this could be perceived, some being green others brown with green spots. 

 Of four pupae of P. Polites L. two, which had developed between dark green 

 citrus leaves in cylinders of clear glass, were of a striking dark green but two, 

 which had pupated in similar cylinders without leaves and whose environment 

 was greyish, were bark-coloured. Both Jacobson and Vosseler obtained similar 

 results with pupae reared completely in the dark and the latter expresses 

 astonishment that in that case such pupae assume the colour of their immediate 

 surrounding. Jacobson suspects that my negative results are due to the fact 

 that my experiments, unlike his, had not been conducted in full daylight. My 

 experiments, however, were certainly not conducted, like his, in the natural 

 state even if under white gauze, although by no means in the dark but in 

 cylinders of clear glass or in boxes covered with white gauze and in rooms 

 of houses where, indeed, subdued daylight only is admitted in order to avert 

 the great heat, but which are, nevertheless, as well lighted as an ordinary 

 mid-european dwelling. Moreover, in complete darkness similar results are 

 obtained as I have just mentioned. There is a great deal, therefore, still requiring 

 elucidation. Before proceeding I would, however, draw attention to one or two 

 points. So far as I can call to mind, and the illustrations in my possession 

 of Memnon pupae confirm this, the green chrysalides of this species are very 

 light, mostly yellowish green and by no means of the dark green of citrus 

 leaves; I also have a recollection that the pupae designated with the rather 

 indefinite term bark-coloured do not exactly conform to the colour of the 

 ligneous parts of the citrus tree. We must not lose sight ot this ; in such 

 matters we must beware of unconscious auto-suggestion. 



A considerable number of observations and discussions on this subject have 

 seen the light. Many of the more important of these were available to me; 

 of a great many others, where this was not the case, I have been able to 

 consult the ample and apposite quotations published by Prof. P. Bachmetjew 

 in his " Expcrimentclle entotnologischc Studien von physikalisch-chemischen Stand- 

 punkt aus". In making use of these great circumspection must be exercised. 

 Many of the experiments have been conducted in so superficial a manner or 

 have reference only to certain animals or conditions that in this respect, where 

 the difference in susceptibility — not only between species but even between 



