REPRODUCTION— CONCERNING EGGS 207 



ground of the two bodies — egg and bird — differ, so each de- 

 mands a special kind of coloration, where this serves. 



With a strange perversity, many who have discussed this 

 question seem to find insuperable difficulties in explaining the 

 lack of protective coloration which obtains in the great majority 

 of coloured eggs. But in such cases, almost without exception, 

 these eggs are deposited in a nest, itself not infrequently a 

 a conspicuous object. This being so, protective coloration 

 avails nothing for the eggs. Where protection for these has 

 become necessary it is the nest which has undergone the neces- 

 sary transformation (p. 179). Yet the question naturally arises 

 as to why such eggs are coloured. If the pigmentation of the 

 shell neither confers protection nor courts destruction, it would 

 certainly almost seem as though it should, in such cases, have 

 disappeared as a result of the cessation of selection. But this 

 by no means follows, since these varied hues may serve other 

 purposes, where they are not actually protective. On the 

 other hand, the coloration may represent a more or less modified 

 form of an earlier protective type, white eggs being due to the 

 action of selection ; and on this last point we have sure evi- 

 dence. But to appreciate this, it is necessary that the broad 

 outlines of the evolution of coloured eggs should first be traced. 



It is almost certain that the eggs of the earliest birds were 

 white, like those of their forebears, the reptiles ; and further 

 since these primitive birds were arboreal, that they were laid 

 in holes of trees or under other cover. Later, when some 

 migrated from the forest region to the plains or meadows 

 colour became necessary : firstly, for protective purposes, and 

 secondly, probably, as a defence against the action of light, 

 which in excess is inimical to protoplasm. It is not really 

 difficult to see how the varied coloration seen in birds' egfcrs 

 to-day may have been evolved, and in all probability egg-eating 

 animals largely aided its development. We may assume that, 

 as in the case of the Sphenodon or Tuatera Lizard of to-day, 

 there was a tendency to develop rust-coloured stains on the 

 shell, some eggs being more decidedly marked in this way than 

 others. Now with the migration to exposed localities, these 

 eggs, unless constantly brooded by one of the parents, would 

 have to remain exposed for longer or shorter periods, when 

 sooner or later various creatures in the new environment would 



