ADAPTATION TO SUKROUNDINGS. 13 



member of the I'lover family {Gharadriidce). In the upper 

 division of the case are shown the eggs, newly-hatched young, 

 and young males and females in the first autumn plumage; 

 as well as old males and females in winter, when both 

 sexes are exactly alike in colour, size alone distinguishing 

 them. The large group occupying the lower part of this case 

 consists of adult birds in the plumage they assume in the breed- 

 ing time (May and June). In the female the only alteration 

 from the winter state is a darker and richer colouring, but in 

 the males there is a special growth of elongated feathers about 

 the head and neck, constituting the " ruff," from which the bird 

 derives its name. In addition to this peculiarity, another, 

 rare among animals in a wild state (though common among 

 domesticated breeds), may be observed, that of striking diversity 

 of colour in different individuals. Of the twenty-three specimens 

 shown in the case no two are entirely alike. 



Next in order stands a case displaying the remarkable Group of wild 

 variations, according to season and age, in the plumage of the ^^^^„ sea- 

 Wild Duck, or Mallard {Anas boscas). The most noticeable sonal change 

 feature in the plumage-changes of this group of birds is the ° ^^^s^- 

 assumption in summer by the males of certain species of an 

 " eclipse-plumage," closely resembling the one worn by the 

 females at all seasons. At other times the males are much 

 more brilliantly coloured than their partners. The eclipse- 

 plumage corresponds to the winter, or non-breeding dress of 

 other birds which have a seasonal change. 



On the same side of the haU follow two cases illustrating cases iilus- 

 the adaptation of the colour of animals to their natural sur- Vf'^+^f j. t 

 roundings, by means of which they are rendered less con- Colour to 

 spicuous to their enemies or their prey. The first contains a conditions'^ 

 specimen of a Mountain or Variable Hare (the common species 

 of the north of Europe), a Stoat, and a Weasel, and some 

 Willow-Grouse and Ptarmigan, as well as an Arctic Pox, 

 in their summer dress, all obtained in Norway, showing the 

 general harmony of their colouring at this season to that of 

 the rocks and plants among which they live. The second case 

 shows examples of the same animals obtained from the same 

 coimtry in winter, when the ground was covered with snow. 

 Such striking changes as these only occur in latitudes and 



