THE VIPEE. 219 



incubation ; jet tlie 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 information proves the same, the 

 reason for incapacity in the cuckoo will be allowed to haye 

 been taken up somewhat hastily. 



Not long after, a fern-owl was procured, which, from its 

 habits and shape, we suspected might resemble the cuckoo 

 in its 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 stuifed 

 hard with large phalance, moths of several sorts, and their 

 eggs, which, no doubt, had been forced out of these 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 intes- 

 tines, 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. 



LETTEE LXXIII. 



TO THE SAME. 



Selborne, April 29, 1776, 

 Deae 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 



but this position cannot be supposed to interfere with the power of incuba- 

 tion, since it occurs al&o in other birds that do incubate, as the owl and 

 Caryocataclea.'''' 



