THE COLORATION OF REEF FISHES 537 



('08), the well-known English hunter of big game in Africa, states 

 that he is quite sure that to a South African Bushman there is 

 in nature no such thing as protective coloration. 



In so far as this remark has reference to the effect of counter- 

 shading (and it must have such reference, since the part is in- 

 cluded in the whole), Mr. Selous is affirming an apparent impossi- 

 bility. The native tracker may be vastly superior to his white 

 master in his ability to interpret certain sense-impressions, but 

 whatever reduces their distinctness militates against his success^ 

 and this is exactly the effect of countershading. For of much 

 light falling upon the darker surface of a strongly countershaded 

 object Uttle is reflected, while of the httle reaching its shaded 

 underparts a mere fraction is absorbed. But, if much subtracted 

 from much and little from little leave the same net result, no 

 eye, savage or civilized, can gather from the appearance of the 

 countershaded object that evidence of its solidity upon which 

 every observer is forced largely to rely. 



Thayer's theory of obliterative coloration was begotten 

 through understanding the necessary effect of countershading. 

 Even if it should appear that errors have been made in its appli- 

 cation it remains an eminent contribution to the literature of 

 its subject; yet Dewar and Finn ('09) fail to review it upon its 

 merits, and justify their reference to it by the fact that it was 

 enunciated in reputable journals, and has been noted with 

 approval by a leading student of the color problem. They 

 intimate that this is an hypothesis based upon the assumption 

 that animals see with an artist's eye. Their view is apparently 

 in part a direct result of Mr. Thayer's over-insistence upon artistic 

 sensibility as a prerequisite to appreciation of the laws of animal 

 coloration. It involves confusion of ideas, however, and failure 

 to distinguish between the necessary effect of countershading 

 upon image-forming eyes, and comprehension of the principle of 

 its operation. 



Countershading appears almost universally upon reef fishes, 

 and its absence, or relative deficiency, seems to be definitely 

 correlated with some unusual habit or peculiar form. The 

 remora (Echeneis naucrates) may have any side uppermost, as 



