tlie Coloration of Eggs. 557 



to the experiments I am about to describe that they were 

 confined to animals that rely greatly on scent, and are, 

 therefore, a less important potential factor in the selection 

 of recognition-coloration than are animals that have to rely 

 on sight alone. 



I might say in conclusion that I have already, in the 

 course of my work, had to throw aside or modify so many 

 tentative explanations for various facts, that I fully expect 

 that much that I have written in this paper will yet meet the 

 same fate at my own hands or that of my critics. Theories 

 are the stepping-stones to knowledge. But not when we 

 refuse to leave them behind us. I shall consider my present 

 suggestions to have amply served their turn if, discarded 

 themselves, they should nevertheless have resulted in an 

 awakened and resultful interest in the explanation of two of 

 the most fascinating and neglected of colour-problems. 



Some further Observations and Reflections. 



Since I wrote the above paper I have had a limited 

 opportunity for further observation and experiment. I will 

 touch briefly on a few of the more interesting results, 

 reserving a fuller account for a future occasion. 



The selective factors in the matter of Cuckoos^ eggs. — I have 

 placed eggs not their own in the nests of a number of birds 

 and watched the result. The first three or four, although 

 contrasting strongly with the bird's own eggs, were accepted, 

 and I expected a repetition of what I rememl)ered as my 

 boyish experience. Subsequently, though many acceptances 

 still occurred, the majority of the changelings were rejected, 

 and Prof. Newton's explanation of the facts with regard to 

 the eggs of the English Cuckoo — " That certain kinds of 

 birds resent interference with their nests much less than 

 others .... but with other species it may be, nay, doubtless 

 it is, different " — was supported. I am delighted to have 

 obtained so unequivocal a result in favour of Mr. Stuart 

 Baker's view on a point on which I was inclined to differ 

 from him; and I am glad to have indicated, at my own 



