168 THE NATURAL HISTORY 



It must be allowed, as this anatomist observes, that the crop 

 placed just upon the bowels, must, especially when full, be in a 

 very uneasy situation during the business of incubation ; yet the 

 test will be to examine whether birds that are actually known 

 to sit for certain are not formed in a similar manner. This 

 inquiry I proposed to myself to make with a fern-owl, or goat- 

 sucker, as soon as opportunity offered : because, if their formation 

 proves the same, the reason for incapacity in the cuckoo will be 

 allowed to have been taken up somewhat hastily. 



Not long after a fern-owl was procured, which, from it's habit 

 and shape, we suspected might resemble the cuckoo in it's 

 internal construction. Nor were our suspicions ill-grounded ; 

 for, upon the dissection, the crop, or craw, also lay behind the 

 sternum, immediately on the viscera, between them and the 

 skin of the belly. It was bulky, and stuffed hard with large 

 phalcence, moths of several sorts, and their eggs, which no doubt 

 had been forced out of those insects by the action of swallowing. 



Now as it appears that this bird, which is so well known to 

 practise incubation, is formed in a similar manner with cuckoos, 

 Monsieur Herissant's conjecture, that cuckoos are incapable of 

 incubation from the disposition of their intestines, seems to 

 fall to the ground : and we are still at a loss for the cause of 

 that strange and singular peculiarity in the instance of the 

 cuculus canorus. 



We found the case to be the same with the ring-tail hawk, in 

 respect to formation ; and, as far as I can recollect, with the 

 swift ; and probably it is so with many more sorts of birds that 

 are not granivorous. 



I am, &c. 



LETTER XXXI. 



TO THE SAME. 



Selborne, April 29, 1776. 



DEAR SIR, 



ON August the 4th, 1775, we surprised a large viper, which 

 seemed very heavy and bloated, as it lay in the grass basking 

 in the sun. When we came to cut it up, we found that the 

 abdomen was crowded with young, fifteen in number; the 

 shortest of which measured full seven inches, and were about 



