400 CUCULIDJE. 



" precisely similar" in structure and position to that of our 

 own bird, and yet those species perform maternal duties. 

 The Author of the present work seems to have thrown out 

 a more valid hint when he suggested first in 1828, in a note 

 in Jennings's ' Ornithologia ' (p. 138), and more fully in a 

 communication to Blyth, printed in his edition of White's 

 'Natural History of Selborne ' (Introd. p. iii.), that the 

 small size of the sexual organs in this bird, and particularly 

 of the blood-vessels which supply them, with the probably 

 low state of excitement consequent thereupon, may diminish 

 the interest attached to the providing for the wants of the 

 young. But it must be borne in mind that in many cases 

 we really know not which is cause and which is effect, so 

 that there is always a risk of mistaking the one for the other, 

 and in the present instance it may be quite as reasonable to 

 suppose that the small size of the organs in question may be 

 the result of diminished parental affection, as the converse. 



To return to the egg of this bird. It has long been known 

 to be variable in colour. This was Jenner's opinion (Phil. 

 Trans. 1788, p. 227), though he was ignorant of the amount 

 of variability attributed to it by former writers, and in recent 

 times the subject has given rise to a long controversy. It 

 may be stated, however, that in this country Cuckows' eggs 

 have scarcely ever been observed to differ to the extent 

 asserted by some foreign oologists. With the exception of 

 two, mentioned by Mr. Cordeaux and Mr. A. C. Smith (Zool. 

 s.s. pp. 1285, 3516), which were blue, British specimens are 

 ordinarily of a pale greyish-green or reddish-grey, more or less 

 closely mottled with darker markings, spots or specks of dif- 

 ferent sizes, and also suffused with patches of a lighter shade. 

 They measure from "95 to *78 by from "78 to '61 in. iElian, 

 who flourished in the second century, declared that the 

 Cuckow did not lay her eggs indiscriminately in the nests of 

 all birds, but only of those that she knew to produce eggs 

 like her own, which from their similarity would thus not be 

 recognized or suspected.* In 1767, Salerne, evidently not 



* This statement has not been accurately represented by some authors who 

 have referred to it, as for example De Montbeillard (Hist. Nat. Ois. vi. p. 309), 



