168 Bird-Song : and Neu) Zealand Song Birds 
and measuring* f in. in length and \ in. in breadth. It is 
described by Buller as greenish-white or very pale olive in 
colour, often clouded or stained with brownish-grey. He also 
mentions one of a pale creamy colour, one pure white, one 
olivaceous-grey, perceptibly darker at the larger end, and very 
minutely granulated with brown over the entire surface. 
Eggs have been found in the nests of other Maori birds than 
the riroriro,—such as fantail, robin, and tom-tit; also in the 
nests of introduced British birds,—the blackbird, chaffinch, 
and sparrow, and Fulton states that the eggs varied "accord¬ 
ing to the host imposed on” (Tr., Yol. 42, 1910, pp. 401-2). 
With reference to the last remark, it has been supposed that 
the extraordinary variation in the coloration of the egg of 
the European cuckoo,—an egg which is also remarkably small 
when compared with the size of the bird,—is explained by its 
parasitical habit; it is said to place its eggs in the nest of the 
bird whose eggs its own most nearly resemble. Until quite 
recently it had not been proved, however, if each hen lays 
eggs of a particular coloration, or if each lays variously- 
coloured eggs. In one instance, it is true, a cuckoo was shot 
as she was leaving the nest of an Icterine warbler, and in her 
oviduct was found an egg very like that of the warbler; and 
in the nest was "an exactly similar egg, which there can be no 
reasonable doubt had just been laid by that very cuckoo.” 
(ND, Yol. 1, p. 122). But surely a reasonable doubt at once 
arises: if one egg had just been laid, the second egg would 
hardly have the shell already formed, and certainly the colora¬ 
tion would not have taken place (See ND, Yol. 1, p. 185). If, 
therefore, the egg in the nest was exactly similiar to the one in 
the oviduct of the bird destroyed, there can be no reasonable 
doubt that the former had been laid by some other bird, and 
not by the one destroyed. 
The difference in coloration of the European cuckoo’s eggs 
is well shewn in Seebohm’s book of British birds’ eggs (SE, 
pi. 49), and the reviewer of the book in the "Pall Mall Gazette” 
(15th Jan., 1897), remarked: "When Parliament was consider¬ 
ing a measure for the protection of the eggs of wild birds, 
