568 Mr. C. F. M. Swynuerton on 



theless well to be clear about it, I find that of the Passerine 

 eggs with markings that I am best acquainted with at 

 Chiriuda, about 15 per cent, show considerable variability, 

 led by Pycnonotus layardi, while 26 per cent, are poly- 

 morphic in a more definite way, each possessing two or 

 more forms that are in themselves very constant and 

 between which intermediates rarely occur. The remaining 

 59 per cent, are really very uniform, apart from rare 

 variations. It must be remembered, too, that even in 

 highly variable eggs there is, in many cases, a common 

 form ; also that monochrome eggs are very numerous and 

 seldom very variable. The percentage of variable species 

 will doubtless be higher in some localities and lower in 

 others. 



The criticism is a very important one, nevertheless, and 

 I will deal further with variability below. 



One might easily go on criticizing. Thus, it might be 

 suggested that it is only in species that do not sit till the 

 clutch is laid, and then only during the first few days, that 

 the matter of egg- coloration will be of importance in 

 rslation to enemies ; after that it is the parents' coloration 

 that will count. But some parents leave their eggs readily 

 on the approach of an enemy, while others are easily 

 driven off from their nests, and the distinctive element in 

 egg-coloration is, in many cases, only regarded as a last 

 line of defence. The objection is as though one should say 

 that the brilliant displays of many insects when finally at 

 bay are not mnemonic, because at all other times the bright 

 surfaces are concealed by dull-coloured tegmina, &c. It 

 might also be suggested, as a criticism, that egg-eaters will 

 sometimes obtain too few eggs to eliminate the indis- 

 criminate craving already referred to. The objection is 

 again a limited one. Or again, that I probably so surfeited 

 my animals with fowls' eggs that what appeared to be prefer- 

 ences were based only on degree of resemblance, in smell or 

 taste, to the eggs oi G alius domesiiciis. Plausible for the 

 mongoose, the criticism* is inapplicable to the rat and lemur, 

 and in any case, it admits a basis of preference. Still, the 



