192 
NATURAL HISTORY OF SELBORNE. 
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 Hon. DAINES BARRINGTON. 
DEAR SIR, Selborne, April 29, 1776. 
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 ab- 
domen was crowded with young, fifteen in number ; the shortest 
of which measured full seven inches, and were about the size of 
full-grown earth-worms. This little fry issued into the world 
with the true viper-spirit about them, showing great alertness 
as soon as disengaged from the belly of the dam : they twisted 
and wriggled about, and set themselves up, and gaped very wide 
when touched with a stick, showing manifest tokens of menace 
and defiance, though as yet they had no manner of fangs that we 
could find, even with the help of our glasses. 
To a thinking mind nothing is more wonderful than that early 
instinct which impresses young animals with the notion of the 
situation of their natural weapons, and of using them properly 
in their own defence, even before those weapons subsist or are 
formed. Thus a young cock will spar at his adversary before his 
spurs are grown ; and a calf or a lamb will push with their heads 
before their horns are sprouted. In the same manner did these 
young adders attempt to bite before their fangs were in being.f 
* This most singular habit of the cuckoo is not to be accounted for upon any structural pecu- 
liarities, as there are genera closely allied to it which incubate their own eggs ; while on the 
other hand the same habit is observable in a bird of a very different family, the " cow-bunting" 
of Wilson, one of the starling tribe. All profferred explanations must therefore fall at once to 
the ground, if not applicable alike to both. — Ed. 
t A still more extraordinary instinct is that which guards an animal against the weapons or 
mode of attack, of an antagonist. This may be noticed in a thousand instances, but in none 
more strikingly than in the manner a rat defends itself from a ferret, being perfectly aware that 
