ASSIMILATIVE COLOURATION. 891 
mammals, and the skin of all the Snakes and Lizards, is of one 
uniform isabelline or sand colour.”* Brehm writes :— “ The 
birds, the reptiles, and even the insects show the same stamp, 
though form and colouring may vary greatly. When any other 
colour besides sandy yellow becomes prominent, if hair, feather, 
or scale be marked with black or white, ashy grey or brown, red 
or blue, such decorations occur only in places where they are not 
noticeable when looked at from above or from the side.” + But 
he also remarks :—‘‘ The fact that almost all the desert animals 
agree in colouring with their surroundings explains why the 
traveller who is not an experienced observer often sees, at first 
at least, but little of the animal life.” {| This appears to better 
illustrate the survival of an original assimilative colouration than 
to afford an example of the strict definition of what is meant as 
‘* protective resemblance,” which affords an extraneous means of 
survival under an increased competition of life. Mr. Beddard, 
discussing the effects of temperature and moisture on the colours 
of animals, considers it “‘ at least possible that the tawny colours 
of desert animals, which have been so often brought forward as 
an instance of adaptation to the hues of their environment, may 
be due to a similar cause.’ § Mr. Quelch, writing on the Birds 
* ‘This,’ vol. i. p. 429. I do not remember meeting with this remark in 
the Canon’s ‘ Great Sahara,’ and it may have been an observation recalled 
when the specimens were more closely examined. Such reflections are no less 
valuable when subsequent considerations. Some exceptions to this rule were, 
however, given by Canon Tristram to Mr. Darwin: ‘Thus the male of. 
Monticola cyanea is conspicuous from his bright blue colour, and the female 
almost equally conspicuous from her mottled brown and white plumage; 
both sexes of two species of Dromolea are of a lustrous black; so that these 
three species are far from receiving protection from their colours; yet they 
are able to survive, for they have acquired the habit of taking refuge from 
danger in holes or crevices in the rocks’ (‘Descent of Man,’ second edition, 
p. 456). According to Dr. Merriam: ‘‘The theory of the direct action of 
environment in modifying colour, as in the bleached types of the desert 
regions, is not borne out by observations, and is disproved in the case of 
nocturnal types” (Balt. Meet. Am. Soc. Nat.; see ‘ Science,’ new ser. vol. i. 
p. 38). Another American authority—Mr. Orr—accepts the theory, and 
remarks :—‘‘ Living matter seems to be in a general way capable to a certain 
extent of photographing colours when exposed for many generations” (‘A 
Theory of Development and Heredity,’ p. 50). 
+ ‘From North Pole to Equator,’ p. 386. t Ibid. p. 331. 
§ ‘Animal Coloration,’ 2nd edit. p. 60. 
