Iviii 
INTRODUCTION. 
larger end^ and the air contained in them communicates with the chicken 
through the fine pores of the membrane, and serves, at the same time, to 
resist the pressure of the surrounding atmosphere, supply it with air, and 
act, most probably, by mechanical pressure on the fluids that are absorbed 
by it.“ We, as well as many other persons, have heard the young bird 
chirrup in the shell ; an act which indubitably proves that it breathes in 
air. When it has attained the state of maturity, it exerts its efforts to 
escape from confinement, by stretching its body, or by piercing the shell 
with its bill. In this operation the patient parent often assists. The 
'^noblei^t parts of the animal rise first into existence, whilst the most ignoble 
members, or those on which its vitality does not depend, receive the vivi- 
fying touch from the hand of nature later in time. This wonderful and 
curious process, which, from a mere speck of jelly-like germ, educes into 
life a surprizing specimen of living organization, arrests our attention. In 
' a few short weeks, the motionless speck, which lay, for a time, concealed 
within a small portion of the compass of an egg, darts unfettered through 
the unbounded horizon, with the rapidity of lightning, or the swiftness of 
the storm ; crosses vast seas in search of subsistence ; roams from empire 
to empire ; or strays from the ice-bound countries beneath the poles, to 
the hot and steaming waters under the line. Birds, in general, except the 
rapacious kinds, prefer the neighbourhood of the habitations of men; 
there, though fear often prevails over their inclinations and appetites, they 
delight to haunt. The Rook, the Blackbird, the Thrush, the Sparrow, 
the Redbreast, the Wren, the Yellow Bunting, the Cirl Bunting, the 
Hedge Sparrow, the Chaffinch, the Titmouse, and the Greenfinch, find 
subsistence in a district, which they leave only when compelled by power- 
Rarely in a wild state do two birds of a different species unite; in general, they are pecu- 
liarly chaste in their loves, but when they overstep their usual boundaries, and take a partner of a 
different species, if the female be impregnated, an intermediate, or bastard, species, is produced ; 
if it be a male, it is supposed to be incapable of propagating descendants similar to itself ; 
and if a female, her offspring soon returns to the colour of the common species. Most natu- 
ralists presume, that, in order to the production of young, by different animals, that they must 
be species of the same genus. 
