204 
[LETT. 
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 the-ir 
formation proves the same, the reason for incapacity in the 
cuckoo will be allow^ed to have been taken up somewhat 
hastily. 
Not long after a fern-owl was procured, which, from its habit 
and shape, we suspected might resemble the cuckoo in its 
internal construction. E'or were our suspicions ill-grounded ; 
for upon dissection, tlie 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 
phalc€7im, moths of several sorts, and their eggs, which no doubt 
had been forced out of those insects by the action of swallowing. 
I^ow 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 
ccmorus. 
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 \vith many more sorts of birds 
that are not granivorous. 
Selborne, 3, 1776. 
ooat-sucker's ego. 
