No. 517] 



NOTES AND LITERATURE 



59 



"may be readily disproved by a careful examination of a few 

 molting specimens. " \\ is also now well known that the white 



blanching of the hairs of the summer coat. In other words, 



entirely to molt. In the case of the hares and weasels the 

 change to white in winter is only partial at the southern border 

 of the ranges of species that further north become wholly white 



group remain practically white in summer, as in northern 

 Greenland and northern Ellesmere Land. The time of molt 

 also varies with the character of the season. As has long been 

 known, an early spring or fall brings on the molt a month or 

 more earlier than a later one. and hence a change of color in 

 such species as have a white winter livery is correspondingly 

 later. 



Mr. Nelson confirms the statements of previous writers that 

 the pelage iti mammals is in other ways subject to modification 

 by the environment, as through variation in its length and den- 

 sity in accordance with the severity of the climate. In discuss- 

 ing the effect of environment, he ;dso eoiifirms the experience 



as well, that "like climatic conditions often produce the same 



mediate borders beyond which new waves arise. When the waves of 

 . . . In the ease of wide-ran.-iii-" suhsperi.-s such fluctuations are in- 



struction bv disease. This is espeeially marked among rodents. 



