594 W. H. LONGLEY 



recognition of its essential truth? Biologists may have been 

 surfeited with theories, and its first presentation ('96 a, '96 b) 

 was certainly inadequate for a concept of such revolutionary 

 tendencies. Still, it never lapsed into obscurity, and has even 

 aroused more opposition in some quarters as its exposition has 

 become more detailed. 



Thayer's work must remain the inspiration — and despair — ■ 

 of many who will eventually accept its main contention. It is 

 full of suggestion of things yet to be done, but the keen eye and 

 cunning hand of a master workman have established an almost 

 unapproachable standard of excellence, and his active mind has 

 anticipated the results of investigation in almost every major 

 field of inquiry within his province. But, with all its merit, it 

 has one fundamental defect, which explains its failure to win 

 general approbation. It is many-sided, yet is predominantly 

 a work of exposition or deduction. As Gerald H. Thayer has 

 it in the introduction to Concealing Coloration: 



For the most part, we do not draw hypothetical conclusions from 

 facts; but we reveal certain beautiful facts hitherto unknown; we dis- 

 close and explain the remarkable power of several naturally applied 

 laws of optical illusion — as these applications stand, by whatever causes 

 produced, and as all may see them. That is, we show and analyse the 

 concealing power of the colors of animals as they exist today. 



That countershading is the prime factor in the etherealization , 

 of solid bodies, is not an abstraction based upon the study of 

 animals of unsubstantial appearance; it is the conclusion of a 

 purely deductive process of reasoning. By shading a plane 

 figure we endow it with the semblance of solidity; by counter- 

 shading a solid object, appropriately lighted, we invest it with 

 unreality, and leave it lacking only fitting background in order 

 to become wholly invisible. A system of countershading ap- 

 pears upon the bodies of animals; hence, and this is Thayer's 

 chief contention, their coloration is obliterative, since it is 

 established upon this principle. This is probably true, but 

 sceptics maintain that the fitness of coloring necessary before 

 the deception may be complete is not proven. 



