162 
EGGS OF BIRDS. 
variety of experiments we have tried on various birds, amongst 
which was the swallow, which has been declared to lay as many as nine- 
teen.* A bird will only lay the usual number peculiar to the species ; 
and if, at the period of incubation, it perceives the nest emptied, it is 
deserted. The link of nature having been broken, the female stimulates 
to love again, and soon brings forward by that stimulus, aided by the 
male fecundity, a new lot of eggs ; never more than the former, and 
usually less, because this is properly a forced production, at the addi- 
tional expense of the vigour of the bird, and loss of animal parts, which 
is the cause of a great variation as to the number of eggs laid by domestic 
fowls, depending entirely on the strength of the constitution, and the 
nourishment of the food. In all animals taken immediately under the 
care of man, the dictates of nature are partly suppressed, their food 
changed, habits and manners altered, and disease often ensues, which is 
the origin of the great variety of colours in reclaimed animals. 
Nature pursues invariably one course ; therefore to draw a general 
rule of her actions we must strictly adhere to her in an unmolested, 
uncultivated state ; for if we deviate from that we must infallibly err. 
We do not mean to say accidental varieties do not take place in animals 
unreclaimed, but such lusus are by no means common ; and when we 
see a bird materially deviate in colour from its species, we may consider 
it as a constitutional defect, that the natural secretions are changed or 
suppressed with which the feathers are dyed. To enter minutely into 
a discussion on this head would swell this article beyond its limits ; 
all we wish is, to point out the necessity of strictly adhering to nature 
for observations on natural causes. A domestic fowl, who will sit for 
six weeks upon an empty nest, is not to be produced as a proof of the 
actions of nature. Will any bird, in its natural wild state, continue to 
sit on its nest after the eggs are taken out ? One egg, indeed, is some- 
times sufficient to produce the act of incubation ; but what is it then that 
prevents the secondary eggs from coming forward, when it is well known 
if a bird is prevented from sitting, she soon resumes her desire of 
propagation natural to every animated being ? Because the very act of 
incubation is the effective cause ; the line which nature has drawn, and 
which the animal by instinct feels. We conceive the production of a 
second lot of eggs to be an extraordinary exertion of nature ; a wonder- 
ful proof of the affection of the all-wise Creator for the preservation 
and continuation of his creatures, and the resources he has furnished 
some animals with, in case of necessity, to prevent the total extinction 
* An assertion of Dr. Lister. Vide Br. Zool. p. 337. 
