14 



CENTRAL HALL. 



Case illustrat- 

 ing Protective 

 Besemblance 

 of Desert 

 Animals to 

 their Sur- 

 roundings. 



Uimicry. 



localities where the differences between the general external 

 conditions in the different seasons are extreme, where the snow 

 disappears in summer and remains on the ground during most 

 of the winter. Even some of the species here shown do not 

 habitually turn white in the less severe winters of their southern 

 range, as the Stoat in England and the Hare in Ireland. In a 

 few permanent inhabitants of still more northern regions, where 

 the snow remains throughout the year, as the Polar Bear, 

 Alaskan Bighorn Sheep, Greenland Falcon, and Snowy Owl, 

 the white coat is retained throughout the year. The white- 

 ness of these animals must not be confounded with albinism 

 (whiteness occurring accidentally in individuals normally of 

 a different colour), illustrated in a case on the other side of 

 the hall. 



The case on the east side of the hall nearest the great 

 staircase contains examples of conformity of general style of 

 colouring to surrounding conditions, as exemplified by some of 

 the commoner birds, mammals, and reptiles of the Egyptian 

 desert, placed on the stones and sand amid which they habitually 

 dwell. The advantage of this colouring in concealing the her- 

 bivorous species from their enemies, and enabling the carnivorous 

 to approach their prey unperceived, is obvious. Many excellent 

 cases of concealment by adaptation to surroundings, especially 

 in eggs and young birds, may be seen among the groups in the 

 bird gallery. 



More special modifications for the same purpose are shown in 

 the adjacent bay on the east side of the hall by insects which 

 closely resemble the objects, such as leaves, twigs, etc., 

 among which they dwell. The close imitation of a dead leaf, 

 presented by the Leaf-Butterfly (Gallima inacJiis), when its wings 

 are closed, could not be surpassed. A further stage of the same 

 condition, called " Mimicry," is where the object resembled, or 

 mimicked, is another living animal, belonging to a different 

 species, family, or even order. The resemblance in these instances 

 is also believed to be for protection, or to be in some way 

 advantageous to the animal possessing it. We know, however, 

 so little of the habits and life-history of animals in a state of 

 nature that many of the purposes supposed to be served by 

 particular colours or appearances can only be regarded at 



