130 MOSTLY MAMMALS 
that such modifications of colour, especially when they 
occur in animals belonging to many widely sundered 
groups, cannot have taken place suddenly, but must have 
been due to very gradual changes as the particular 
species adapted itself more and more completely to a 
desert existence. 
To obtain an idea of the type of coloration character- 
istic of the smaller desert animals, the reader cannot do 
better than pay a visit to the Natural History branch of 
the British Museum, where, in the Central Hall, he will 
find a case devoted to the display of a group from the 
Egyptian desert, mounted, so far as possible, according 
to their natural surroundings. 
Among such animals may be mentioned the beautiful 
little rodents respectively known as jerboas and gerbils, 
together with various birds, such as sand-grouse, the 
cream-coloured courser, the desert-lark, desert-finches, and 
desert-chat, and also various small snakes and _ lizards, 
among the latter being the common skink. Although 
some of the birds retain the black wing-quills of their 
allies, in all these creatures the general tone of coloration 
is extremely pale, browns, fawns, russets, olives, greys, 
with more or less of black and pink, being the pre- 
dominant tones; and how admirably these harmonise with 
the inanimate surroundings one glance at the case in the 
Museum is sufficient to demonstrate. Very significant 
among these are the desert-finches (Exythrospiza), which 
belong to the brightly coloured group of rose-finches, 
one of these specially modified species ranging from the 
Canaries through the Sahara and Egypt to the Punjab, 
while the second is an inhabitant of the Mongolian desert. 
Among larger animals, a considerable number of the 
gazelles are desert-dwellers, these including the palest- 
