XLIII 



hypothesis by which the bearing of the phenomena of life can only be partly 

 explained. While this theory may, in itself, not be so impossible, as Meldola 

 and PouLTON appear to think, it can only be applied in connection with the 

 evolutionary changes to which the colour as much as the whole form of each 

 animal is subject and which may differ considerably not only in the greater 

 divisions but even in individuals. Where it does not take this into account I 

 believe consequently that it cannot lead to the desired goal and that all investig- 

 ations and observations conducted from this point of view lead a priori on 

 the wrong track. Even resemblance of the colour of pupae to their environ- 

 ment, the conception of so-called bark-colour, must be studied with greater 

 attention, since a great deal of superficial observation has been brought to bear 

 on the subject; moreover, the same remarkable agreement observed in many 

 larvae has to be studied more accurately and may prove ot great service for 

 comparison in this connection. Nearly alle observations noted in this respect 

 have taken place far too much under the suggestion of mimicry to allow of 

 an unbiassed judgment being formed. It should, therefore, be borne in mind 

 that this resemblance to the environment occurs, not only as regards colour, 

 but equally as regards shape, as for instance in the case of the larvae of 

 geometrae resembling twigs, which can hardly be attributed to the influence of 

 light rays. Moreover, chemical and microscopic investigation is indispensable 

 here. We know that the colours of imagines, except such white as is produced 

 by the filling with air of the scales, are of a pigmental or structural nature. 

 We know something about these pigments but our knowledge is still very 

 incomplete, and as regards the occurrence of structural colours too we are as 

 yet very ignorant. Without a doubt pigmental colours occur in caterpillars 

 but others exist also even on a large scale, but what do we know of these? 

 And as regards the pupal colours, observation leads us to suspect, indeed, 

 something similar but concerning their structural colours too we know practically 

 nothing. Our knowledge generally with regard to these colours in still extremely 

 insignificant. I have already referred to this at the conclusion of the chapter on 

 the influence of light in my work '' Noch eiiima/ Mimicry, Selektion, Danvinis)iiits" , 

 published in 1907. A considerable amount of specific and accurate investigation 

 is still needed in this respect. Only then shall we make further progress with 

 the interpretation of the colour phenomena in the pupae of lepidoptera. 



Even the urgent recommendation of further study in this field on these lines 

 has its value; with this I propose, therefore, to terminate my reflections. 



