LETTER XXX. 



SELBORNE, April yd, 1776. 

 EAR SIR, Monsieur Herissant, a French anato- 

 mist, seems persuaded that he has discovered the 

 reason why cuckoos do not hatch their own eggs ; 

 the impediment, he supposes, arises from the 

 internal structure of their parts, which incapaci- 

 tates them for incubation. According to this 

 gentleman, the crop, or craw, of a cuckoo does 



not lie before the sternum at the bottom of the neck, as in the 

 gallin<e, columb<e, &c., but immediately behind it, on and over the 

 bowels, so as to make a large protuberance in the belly.* 1 



* "Histoire de 1'Academie Royale," 1752. 



1 There is nothing whatsoever in the structure of the cuckoo to prevent its 

 hatching its own eggs. The whole question of the curious parasitism of cuckoos 

 and some other birds (such as ZMolothrus) has since been fully elucidated by 

 Darwin. ED. 



