1909] ' Proceedings. ^9 



subspecies of these animals, and to the importance of the subject as 

 affording a key to some evolutionary phenomena. 



He then gave a short resume of the division of colors into groups, 

 structural and pigmental, the subdivision of the latter into lipochromes 

 and melanins and the supposed origin of these pigments. The im- 

 portance of the melanins was mentioned, comprising most of the pig- 

 mental colors found in these two classes of animals other than the reds 

 and the yellows and also forming the basis of many structural colors 

 whose iridenscence is displayed against the dark back-grounds formed. 



The antithesis of melanin, or black, is white which with a few 

 rare exceptions is structural and is explained as due to the fine gran- 

 ular structure of the feather or hair, in which each grain is supposed 

 to lie enveloped in air or gas which breaks up and reflects the light 

 in every direction. While these grains usually are colorless they are 

 not always so. Examples of the effect of fine comminution of ice, glass, 

 black slate etc., were referred to as familiar examples. This whiteness 

 being constant from any angle of view fell under Gadow's group of 

 objective structural colors in distinction to his subjective structural 

 colors in embracing the changeable or iridescent colors. 



The importance of an understanding of the factors that determine 

 color changes because of connection with its evolutionary significance 

 was mentioned and attention was called to the fact that some of the 

 very early mammalogists recognized a transition from melanism in the 

 tropics to albinism in the arctic region coupled with a great increase 

 in size of what they considered one species of bear. 



He then quoted at length several passages from F. A. Allen's essay 

 "On the Mammals and Winter Birds of East Florida, etc.," showing 

 that this author at that comparatively early date (1871) recognized 

 that the geographical variation in color of birds was due to climatic 

 differences and that the greatest factor in this was humidity ; the more 

 humid the region the deeper, and the more arid the locality the paler 

 the colors. Mr. Ward then referred to recent experiments carried on 

 by C. W. Beebe at the New York Zoological Gardens which showed 

 that melanistic changes could be produced during the life of the indi- 

 vidual bird by subjecting it to an abnormal degree of humidity. 



The melanistic and albinistic tendencies were considered by the 

 speaker as more important than sporadic cases of complete albinism or 

 melanism, which were considered probably pathologic in nature. 



