552 Mr. C. F. M. Swynnerton on 



It will not follow that equally conspicuous eggs are 

 equally nauseous, or vice versa. A good counteragent might 

 enable the highest conspicuousness to be selected ia a but 

 slightly deterrent egg, while a far more deterrent egg 

 without other counterag-ents, yet insufficiently deterrent to 

 make up entirely for their absence, might have to be to 

 some extent concealingly coloured. 



4. Colour -groups. — In spite of much general diversity, we 

 find that a number of the eggs of a given area tend to fail 

 into definite colour-groups. If the suggestion that nau- 

 seousness is present in eggs be correct, it is possible that 

 occasionally a colour-group may be to an appreciable extent 

 in the nature of such a mimetic association as I have defined 

 above. The model for one such association (white with 

 pink spots, occurring mainly in holes and domed nests) 

 might be in Europe the eggs of the Tits. My mongoose 

 showed a dislike for those of Parus major. The model for 

 another group, which also figures strongly in holes, might 

 conceivably be provided by the eggs of Picarian birds, most 

 of which are white and are laid in holes. I have no actual 

 evidence here, except for the eggs of Colius striatus^ placed 

 low by my rat. Adult Woodpeckers of three genera were 

 placed very low by my animals "''■. 



The fact that white eggs in holes are a strong group 

 might be accounted for sufficiently by the fact that some 

 powerful families that tend to lay white eggs whether they 

 nest in holes or not (as Picarian birds and Owls) do, actually, 

 lay most often in them. Omit such cases (in which white- 

 ness is probably now mainly a matter of affinity, though 

 the laying in holes may have been, in its origin, either a 

 cause or a result of the whiteness and synaposmatic advan- 

 tage may also sometimes now be present) and relatively 

 little is left to account for. Mimicry may partly account 

 for the white of some of the unrelated members of the 

 group, and an additional explanation for the colouring of 



* That a Woodpecker possesses figliting-weiglit must not, however, 

 be overlooked. Mr. AVallis mentions the case of a squirrel found dead 

 by a friend of his in a Woodpecker's hole, with its skull split. 



