230 Mr. Jenner’s Obfervations on the 
having found it pofleflfed of a capacious ftomach with a thin 
external covering, concluded that the preflure upon this part, 
in a fitting pofture, prevented incubation. They have not 
confidered that many of the birds which incubate have fto- 
machs analogous to thofe of Cuckoos : the ftomach of the 
Owl, for example, is proportion ably capacious, and is almoft 
as thinly covered with external integuments. Nor have they 
confidered, that the fiomachs of nefilings are always much 
diftended with food ; and that this very part, during the whole 
time of their confinement to the neft, fupports, in a great 
degree, the weight of the whole body ; whereas, in a fitting 
bird, it is not nearly fo much prefled upon ; for the breaft in 
that cafe fills up chiefly the cavity of the neft, for which pur- 
pofe, from its natural convexity, it is admirably well fitted. 
Thefe obfervations, I prefume, may be fufficient to fhew 
that the Cuckoo is not rendered incapable of fitting through a 
peculiarity either in the fituation or formation of the ftomach ; 
yet, as a proof ftill more decifive, I Ihall lay before you the 
following fadt. 
In the fummerof the year 1786 , 1 faw, in the neft of a Hedge- 
fparrow, a Cuckoo, which, from its fize and plumage, appeared 
to be nearly a fortnight old. On lifting it up in the neft, I 
obferved two Hedge-fparrow’s eggs under it. At firft I fup- 
pofed them part of the number which had been fat upon by 
the Hedge-fparrow with the Cuckoo’s egg, and that they had 
become addle, as birds frequently fufter fuch eggs to remain in 
their nefts with their young ; but on breaking one of them I 
found it contained a living foetus ; fo that of courfe thefe eggs 
rauft have been laid feveral days after the Cuckoo was hatched, 
as the latter now completely filled up the neft, and was by 
2 this 
