the Coloration of Eggs. 571 



cases to that special constancy wliich one would rather 

 expect to be necessary as a counteragent to the results 

 of any serious diminution of the colour-population. The 

 explanation offered is not incompatible with the view that 

 the phenomenon may be Meudelian. Rather, it perhaps 

 enables us to picture how the necessary basis in heredity 

 for the production of Meudelian results might some- 

 times have been brought about indirectly by selection 

 elimination. 



As for slackness of selection in relation to recognition 

 characters, several things might bring about such a con- 

 dition. An egg that through the present-day specialization 

 of its enemies or its own loss of nauseousness had become 

 completely acceptable to the former could gain no further 

 advantage from recognition and might vary unchecked. 

 The explanation should be particularly applicable to eggs, 

 for these do not possess those other defences, often slight, 

 yet deterrent to attack by weaker or more replete enemies, 

 of known agility, wings troublesome to remove, chitin 

 a trouble to break up completely, and so on, that are 

 commonly present in the highest-grade insects (except, 

 especially, various geometrid larvae, themselves often highly 

 variable) and that, as I have actually seen, render easy 

 recognition still useful to them. 



Again, there is the case (already suggested) of the bird 

 that has taken to nesting year after year in the same spot 

 in great open colonies. Its enemies would no longer consist 

 of chance passers-by and searchers. On the contrary, the 

 existence of the colony would have become a matter of 

 notoriety and attraction to every enemy in the neighbour- 

 hood and far around. Such an enemy would visit the 

 nesting-places whenever it felt hungry enough for a feed 

 of the eggs, the qualities of which it would know well. It 

 would recognise them, not by their coloration, but by their 

 mere presence in the colony, and variation in coloration 

 might once more ensue unchecked. Even if another species 

 with eggs of a different grade should lay in the same colony, 

 the difference in size or shape or texture or general type of 



