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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