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INTRODUCTION. 
hours is, in most instances, sufficient to surround the yolk in the uterus 
with the albumen and shell. But nature seems to have denied to tne Cuckoo 
the power of producing eggs in such quick succession; probably many 
days intervene, as to her, between the production of the first egg, and the 
succeeding one, as the eggs in the ovary, at the time when the female Cuckoo 
is ready to lay, do not follow of a gradual size ; the primary ones in the 
chain, or those which seem to be fecundated by the male, are irregular 
and disproportionate.^" Perhaps this is the cause why the Cuckoo makes no 
nest; and as she would naturally feel no desire to incubate before she had 
deposited her first string of eggs, and as many days, nay, probably weeks, 
might pass away, before the last of the number fecundated would be 
produced, the prior egg, from the lapse of time, might be rendered 
inefficacious for incubation. The egg is divided into two parts, the 
vitellus, the yellow part or yolk ; and the albumen, the double coat of 
white fluid ; the former is surrounded by a thin film without blood-vessels, 
and then by the albumen, which is separated from the vitellus by a thin 
membrane.^® Both the vitellus and the albumen are internally surrounded 
by a fine, but strong film, and externally, by an hard and testaceous sub- 
stance, called the shell. This, in the eggs of some birds, as in the galli- 
naceous tribes. Pigeons, Woodpeckers, Martins, and Swifts, is white on 
the exterior surface ; and in those of most other kinds, either of an uniform 
colour, or tinged or painted with streaks, patches, or spots. All eggs are 
The cause assigned by Monsieur Herissant cannot be the reason of the non-incubation of 
the Cuckoo. He adverts to its internal anatomy, and mentions the peculiarity of its stomach 
resting far back on the abdominal viscera ; but such, in this respect, being also the conformation 
of the Goat-sucker, the Rook, the Bittern, and many others, it consequently follows, 
that as these birds incubate, it cannot be fairly assigned as the cause of the Cuckoo’s non- 
incubation. 
I have seen an hen’s egg of the shape of a lozenge, and some eggs from domestic fowls, 
as small as filberts, others nearly as large as the eggs of the goose ; and I have found eggs in the 
nests of the Hedge Sparrow, Robin, and Blackbird, and of some other birds, greatly inferior to 
the common size. 
