It is very natural for us to ascribe to reason those actions of other animals which would be ascribable to reason, if performed by man. "If," says Keller, (an old German writer,) "the fly be enabled to choose the place which suits her best for the deposition of her eggs, (as, for instance, in my sugar-basin, in which I placed a quantity of decaying wheat,) she takes a correct survey of every part and selects that in which she believes her ova will be the best preserved and her young ones well cared for." The fly, in this instance, apparently exercises an intelligent choice; but does any one doubt that the selection she makes is determined wholly by a blind, uncalculating instinct? The beaver selects a site for his dam at a place where the depth, width, and rapidity of the stream are most fit. There is a tree upon the bank, and food and materials for his work in the vicinity. If a man should attempt to build a beaver's dam, he would abstractly consider all these elements of fitness. The outward manifestations of the quality of abstraction are equally observable in either case. But we must not hastily conclude, because the beaver in one instance acts in a manner apparently reasonable, that he has any reason of his own; for, when we come to study the habits of this animal, we find that he displays all the characteristics of the instinctive principle. If animals are endowed with instincts which apparently act so much like reason in the ordinary course of their operations, we should not at once conclude that there is any need of endowing them with a modicum of reason to account for their deviations from this course, which do not outwardly resemble the acts of reason any more strongly. And besides, it is said, that, if we refer the variations to an intelligent principle, we must refer the ordinary conduct to the same principle. To use an old illustration,--if a bird is reasonable and intelligent, when, on perceiving the swollen waters of the stream approach her half-finished nest, she builds higher up the bank, she was intelligent while making her first nest, and was always intelligent; for how otherwise, it is asked, could she know when to lay down instinct and take up reason?