COLOUR fN LEPIDOPTERA. 9 



Spuler before, seems to have escaped my. attention then, 

 that the pigment in the wings of butterflies is found in 

 two different forms, mostly simply diffused through the 

 chitin, but sometimes also in the form of granules. Remark- 

 ably enough this seemed to uphold my conjecture offered 

 without my being acquainted with this fact, on pages 115 

 and 116 of my paper, that the changes of colour in but- 

 terflies might be brought about by a mere mining or sifting 

 of pigment granules mostly in a chemical yet also some- 

 times in a mechanical way. So this seems to be possible 

 after all. Dr. J. Urech's and other students' continued ex- 

 periments in exposing pupae to a high or low temperature 

 and the chemical-biological deductions therefrom, published 

 by Dr. J. Urech '), although interesting, have not produced 

 any thing decisive against my views. Unless indeed the 

 fact that some rarely occurring colour-aberrations can be 

 brought about by the immediate influence of abnormal 

 conditions of temperature causing for instance an extra- 

 ordinary formation of dark pigment or a chemical shifting 

 of any other one. This I feel obliged to admit. But with 

 reference to the ontogenetical and phylogenetical study of 

 colour-evolution I cannot think it of much value. It will 

 never do to conclude from such abnormal facts, never or 

 only exceptionally occurring under natural conditions, with 

 single individuals, that where in its normal development 

 an increase of dark pigment occurs, this must be caused 

 by an alteration of the temperature and its direct influence. 

 The fact that the human skull can be artificially deformed 

 and this even being a general custom with some wild tribes, 

 cannot be of any valuable account in explaining the origin 

 of dolichocephalism or of brachycephalism of human skulls^). 



1) Ergebnisse von Temperatur-Experimenten an Vanessa lo L. (lUustrirte 

 Zeitschrift fiir Entomologie, 1898). 



Kenzeichnung und kritische Bemerkungen über Terminologisches, Warmeener- 

 getisches und Farbenevolution meiner erzielten Aberrationeu von Vanessa lo 

 und urticae (Zoologische Anzeiger, XXII Bd., n° 582, 13 Miirz 1899). 



2) It is just the same with all similar investigations, being high fashion now- 

 a-days. I recommend reading on this subject Dr. Grafin M. von Linden's Ver- 



!Xotes irom the Leyden Museum, Vol. XXII. 



