Eimer is convinced that the little foundling of a cuckoo has so good a memory of its foster-parents and of the nest in which it was reared, that it is able to make a proper choice of both when it comes to lay its eggs in after life, and further that the experiences of its early youth have "at last become instinctive by inheritance." It can not build a nest because it has never learned how, and if it never builds it can not of course transmit the instinct of nidification. When its original progenitors adopted their piratical methods, they did so with their eyes open, for they acted from "reflection and with design." The male cuckoos are dissolute vagabonds and the females as bad or worse, for they wander about not so much to find nests to steal, as to appease "their insatiable sexual desires."
That some instincts, in both arthropods and vertebrates, have not perceptibly changed from age to age is not to be doubted. As Sidney Smith observed, the wonderful instincts of animals seem to have been given them for the preservation of their species, and that without them they would have long ago perished. He says:
The bee that understands one particular kind of architecture so well, once out of his own special line of business, that of making honey, is as stupid as a pebble stone, and with all his talents only exists that we may eat his labours, while poets sing of them; or he constructs his boasted edifice for an egg of which he knows neither the meaning nor the object, to produce a grub of which he can form no possible conception; whereas man knows the beauty of every brick he lays, or tower that he builds. The bee now builds just as he built in the days of Homer; the bear is just as ignorant of good manners as he was two thousand years ago, or ages ago; the baboon still as unable to read and write as persons of honour or quality were in the days of Queen Elizabeth; but there is no progress among the three B's, whereas now among all classes of men those who can read and write are to be counted by the millions.
We might add that the European cuckoo seems to have been no less adept in stealing nests in the time of Aristotle than it is at this day, and that even among the most rational, adaptable, and most plastic of living beings, in his humblest estate, progress has been but little greater.
II
In some of the fishes, in reptiles, and more particularly in the birds, we can discern the early if often halting steps of that intelligence which in the highest of the primates was destined to turn the world upside down. We can not attempt to specify with any detail the structure of the avian brain, nor would it be of any use to do so, unless we could award the proper functions to its several parts. While this can not now be done, psychology has already learned some valuable lessons from anatomy, at the hands of such a master as Edinger, and is destined to learn many more. Without doubt, in the future, knowledge of the brain of the fish, of the reptile and of the bird will serve as primers for the understanding of the cerebral cortex.
