The Making of Species 
No observer of nature can have failed to 
remark how the least movement on the part 
of an animal will betray its whereabouts, even 
though in colouring it assimilates very closely 
to the environment. So long as the hare squats 
motionless in the furrow, it may remain un- 
observed, even though the sportsman be search- 
ing for it; but the least movement on its part at 
once attracts his eye. Thus, in order that pro- 
tective colouration can be of use to its possessor, 
the latter must remain perfectly motionless. But, 
in tropical countries, where flies, gnats, etc., are 
a perfect scourge, no large animal is, when 
awake, motionless for ten seconds at a time. 
The tail is in constant motion, flicking off the 
flies that attempt to settle on the quadruped. 
The ears are used in a similar manner. Thus 
the so-called protective colouring of herbivora 
cannot afford them much protection. It is 
further worthy of note that the brush-like tip 
to the tail of many mammals is not of the same 
colour as the skin or fur. It is very frequently 
black. Thus we have the spectacle of a pro- 
tectively coloured creature continually moving, 
as if to attract attention, almost the only part of 
its body that is not protectively coloured ! 
Many species of birds display what is known 
as seasonal dimorphism, still more display sexual 
dimorphism. 
Seasonally dimorphic birds very often assume 
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