44 The Oologists' Record, June i, 1922. 



the descendant on the maternal side of generations of Robin 

 Cuckoos, but has an inherited instinct to seek out Robins' nests 

 and make Robins, so to speak, her preferential victims, it ceases to 

 surprise us that the respective eggs of Robin and Robin Cuckoo 

 should exhibit a marked similarity. What has been the law of the 

 survival of the fittest, from the Cuckoo's point of view, throughout 

 the ages of evolution, is thus dovetailed with the line of least resistance 

 on the part of the Robin." But the followers of Mendel will be 

 appeased by the next paragraph, for the author continues : — 



" But I frankly admit that this theory must fall to the ground, 

 if it is a fact that the influence of the male parent bird is at least as 

 potent, if not more so, as that of the female parent on the offspring — ■ 

 and even on the eggs — produced by their daughter. Yet again, it 

 may prove to be the fact that the male Cuckoo tends to associate 

 only with female Cuckoos of his own type, i.e., those reared by the 

 same species of fosterer. This idea may some day turn out to be 

 less fanciful than it sounds — that there is, at present, an unknown 

 but nevertheless definite distinction between the different types 

 of Cuckoo, according to the foster-parents by which they were 

 bred and to which they are attracted." 



These theories open up a wide field for further investigation, 

 but one that is not easy to pursue. After the flood of light shed 

 on the habits of the Cuckoo by the author it would not seem 

 improbable that some of these points may be lifted out of the 

 theoretical stage in the near future. 



Perhaps the main result of Mr. Chance's investigations is the' 

 recording of enough indisputable evidence to support his theory 

 that "a dominant hen Cuckoo, by a process of watching and 

 searching, discovers, some days in advance, the nests of those dupes 

 in which she intends subsequently to deposit an egg." He contends 

 " that the watching of her dupes engaged in building stimulates 

 her own reproductive organs and the resulting egg is ready for 

 extrusion about five or six days afterwards. It follows that within 

 reasonable limits the number of eggs she lays is regulated by the 

 number of suitable nests discovered, though of course, in cases of 

 emergency, a Cuckoo will sometimes make use of what are, to her, 

 unnatural fosterers." 



His theory that the building of a nest by a prospective acceptable 

 fosterer is likely to stimulate the reproductive organs of the Cuckoo 

 may not be generally endorsed ; but the author does prove, without 



