the Coloration of Eggs. 549 



or less formidable or pugnacious parents, perhaps pr )mpt 

 sitters, others Lave close-sitting parents with concealing 

 coloration, others again are covered in (whether in a hole, 

 a domed or deep nest, or the interior of a dense thicket) — 

 or covered merely when left ; and it is these and other 

 counteragents, as we may call them, to conspicuousness 

 that, separately or in combination, have enabled them to 

 develop or retain the latter quality in their coloration — 

 white or spotted, or vivid blue, or (like Barratt's Bulbui) a 

 glorious pink — and so on ; a conspicuousness that, without 

 the couuteragent, might have rendered them liable to 

 detection from some little distance. 



Against these conspicuously-coloured eggs we must place 

 those which, lacking counteragents to conspicuousness, and 

 liable themselves to be first seen were they conspicuous, 

 are, instead, protectively coloured — as those of Plovers. 



So far, this is Wallace^s explanation, but with the col- 

 oured conspicuous eggs added to the yet more conspicuous 

 white. It explains the procryptic element in those eggs in 

 which that element is present, and it explains how the others 

 can afibrd to be conspicuous. It does not explain the latter's 

 coloration. Nor does it explain all cases of relative con- 

 spicuousness i)i nests. 



Missing counteragents * may help to explain some of 

 these cases. But the great missing counteragent, capable 

 of aiding heavily in the explanation of such cases — and of 

 many others — is likely to be some degree of indigestibiiity 

 (or " uauseousness," or " unpalatability ^^) in the egg 

 itself. That some degree of indigestibiiity (it need not be 

 of the most marked order if other counteragents are present 

 to complement it) may be the partial explaration of, for 

 example, the survival of the conspicuously-laid white eggs 

 of some Colics and Doves, and of the often very fairly con- 

 spicuous nests of Bulbuls, Shrikes, &c., w as suggested by my 

 experimental results. 



* Of these, fecundity and perseverance in face of persecution may be 

 one, hardness of shell in relation to certain enemies another, out- 

 balancing advantages at another stage (as of food and " mentality " — 

 Wallis) a third. 



