604 R. S. LULL VARIATIONS OR SPECIFIC DISTINCTIONS: WHICH? 



however, have been based on seasonal condition of the pelage, which causes 

 marked color change. 



But the paleontologists are not concerned with fur and feathers, and I 

 am now inclined to believe that they are not such great offenders in the 

 multiplication of non-existing species as are their recent zoological col- 

 leagues, especially when one realizes the fact that any fauna, as the verte- 

 bratist knows it paleontologically, may cover hundreds of generations as 

 compared with tens or even fewer of living creatures. There is need, 

 however, of more consideration of these several aspects of variability and 

 a keener visualizing of habitat limitations and life conditions, if our 

 descriptive work is to have a lasting value. 



