INTRODUCTION^ 
Iv 
white within. The external paintings on the shells of the eggs of the 
Sparrow-Hawk, Kestrel, and most of the carnivorous kinds, may be 
effaced by slight attrition ; but the colouring of the eggs of the Hedge 
Sparrow, the Whinchat, and of most of the Sparrow tribe, is durably 
imprinted. The yolk, at first, before it descends from the ovary, is without 
the double white, which we have before mentioned. It is in the uterus 
that it is first surrounded by it. At the ends, or extremities of the exterior 
vitellus, are two little, white, flaccid ligaments, called the chalazre, or 
cords, connected with the membrane that lines the shell ; they are 
twisted, small and round, next the yolk, and terminate in a fringe-like sub- 
stance.^^ They are evidently formed from the membrane that encloses the 
yolk. Willughby, P*.ay, and Derham, supposed, that they were intended 
to keep the smaller part of the yolk, in which lies the cicatricula, or 
couch, of the incipient animal, always uppermost, that it might receive a 
greater portion of the incubating heat : but this assertion Haller denies, 
and avers, that the animated being is found indifferently below, as well as 
above. As the hen, during her period of incubation, turns her eggs, this 
action corroborates, in some measure, the opinion of Haller ; because it 
cannot be material to the formation of the chicken, whether the cicatricula 
recover its position from the action of the chalazae, or the care of the Hen. 
The lenglh of time, in which any of the feathered race becomes effete and barren, has not 
as- yet been ascertained 5 but I am inclined to believe, from numerous observations, that birds con- 
tinue to lay much longer than the period commonly supposed. A hen, belonging to myself, was 
killed by accident, whilst laying, after she had been in my court seven years ; and she laid within 
three days after she was first brought thither. When she was killed, there still remained a string 
of fifty eggs at least in the ovary, and I have now a small egg in my possession, almost of a 
lozenge form, which was laid in the year 1703, by a hen, (as I was informed by a friend of 
undoubted veracity) then eighteen years old. I have dissected several female Goatsuckers, and 
I found in the ovary of one of them sixty-three eggs, in that of a W'ater Hen upwards of an 
hundred; and fifty in the ovarium of a Kingfisher. I have commonly found the string of eggs 
in the ovaries of most birds so great in comparison with the number usually laid by them in a sea- 
son, that I strongly Incline to think, that the greatest part of the feathered race would be fruitful 
till within a short period of their natural extent of life. 
