COLORATION AFFECTED BY THE ENVIBONMENT. 71 



brilliant golden yellow, glossed over in the male with purplish 

 black in front." 



In many birds there is a corresponding difference in the 

 summer and winter plumage, which may be more or less 

 marked. Any ornithological work will furnish abundant 

 instances of such colour changes, which are, in many cases at 

 least, not of such a nature as to suggest any advantage in the 

 way of protection, etc. Indeed, the change of colour is some- 

 times a merely incidental result ; part of the feathers break 

 off in the spring, and the colours of the deeper parts of the 

 feather are thus brought into view, which frequently brings 

 about a marked alteration in the tints and patterns of the bird ; 

 this change is of course comparable to the change from a 

 thicker winter to a thinner summer coat in many mammals. 



The snow bunting is whiter at one season of the year than 

 at the other ; but curiously enough the change is precisely the 

 reverse of what one would expect. It is whiter in summer 

 instead of in winter. 



The grey phalarope undergoes as marked a change from 

 season to season as is shown in any animal ; in the winter it 

 has a grey-and-white plumage which closely resembles that of 

 a gull. In the summer it is coloured with various shades of 

 brown. 



Some of these and similar colour changes, which appear to 

 correspond to the seasons, may have some connection with the 

 renewal and decadence of sexual activity. 



Seasonal Change in Ortlioptera. 



Leydig has called attention to the change of colour exhibited 

 by the green grasshopper: in the autumn it becomes yellowish 

 red. A change of this kind might be set down to natural 

 selection; as the foliage becomes yellow a corresponding 



