productive. It fits his central nerve-system for the most complicated functions; it sharpens his senses, and by it his mind, reacting upon itself, is enabled to augment its own elasticity and versatility. Returning to our starting-point, we ask, Is not this one of the means, perhaps the principal one, by which the collectivity of living existence becomes a self-improving machine? As to the crystal, the parts of like structure and properties composing it; as to the whole organism, the elementary organisms whose life makes up its life, so are related to the whole of organic nature the single living existences, that is, the properties and functions of the whole are the sum of the functions and properties of the individuals; and if the individual living being is improved by exercise, does not this also sufficiently explain the progress of the aggregate? Lucid as the supposition appears, on a nearer trial it encounters serious difficulties.
First, only the most highly organized animals are amenable to exercise, or, what means the same thing, trainable. After the generally distributed companions of man, the horse and the dog, the most teachable animal is the elephant. Chamisso found intercourse with the apes on board the Rurik uncommonly instructive, "for," as Calderon says of the ass, "they are almost men," and he made the profound remark that they might be able to bring themselves up to the mark if they did not lack the property which Newton held to be one with genius, steadfastness. Carnivores, with the exception of the cheetah (Felis jubata), ruminants, and rodents, exhibit only moderate teachability; yet Herr Fritsch considered the draft-oxen at the Cape of Good Hope wiser than the horse, and in Brazil and Thibet sheep are trained to carry loads. Among the birds, the higher ones are the parrots, starlings, bullfinches, and canary-birds; the falcon ranks with the cheetah in teachableness. Chameleons, snakes, and carp are only moderately teachable. The training of fleas is only apparent; they always perform their tricks under a kind of compulsion. The immense host of other creatures all around us show no more aptitude for training than they do, for the reason that every animal within its own circle has no need of instruction; what we call instinct affords to animals, without effort of the individual, more than any exercise can. What practice could teach birds to build warmer nests, to find the way south more certainly,-or bees to solve their geometrical, spiders their mechanical problems? Instinct and perfectibility complement each other as it were in the ascending series of animals to a growing sum, so that, the more instinct retreats before perfectibility, by so much does the living being stand at a higher stage. Secondly, although the animals we have named, and many others besides, are susceptible to exercise and trainable, animals still do not of themselves exercise and perfect themselves, but do so only when man takes them to school. Therefore, the animals around him appear less susceptible to training, the lower the stage at which he himself remains. Higher races of men would
