the ruminants, from the ruminants to the pachyderms, and from these again to the beasts of prey and finally to the _quadrumana_, and anatomy shows a gradual development of the brain in similar order which corresponds to this result of external observation. (According to Flourens and Fr. Cuvier.)[236] Among the reptiles, serpents are the most intelligent, for they may even be trained; this is so, because they are beasts of prey and propagate more slowly than the rest--especially the venomous ones. And here also, as with the physical weapons, we find the will everywhere as the _prius_; its equipment, the intellect, as the _posterius_. Beasts of prey do not hunt, nor do foxes thieve, because they have more intelligence; on the contrary, they have more intelligence, just as they have stronger teeth and claws too, because they wished to live by hunting and thieving. The fox even made up at once for his inferiority in muscular power and strength of teeth by the extraordinary subtility of his understanding. Our thesis is singularly illustrated by the case of the bird _dodo_ or _dronte_ (_didus ineptus_) on the island of Mauritius, whose species, it is well known, has died out, and which, as its Latin name denotes, was exceedingly stupid, and this explains its disappearance; so that here it seems indeed as if Nature had for once gone too far in her _lex parsimoniæ_ and thereby in a sense brought forth an abortion in the species, as she so often does in the individual, which was unable to subsist, precisely because it was an abortion. If, on this occasion, anyone were to raise the question as to whether Nature ought not to have provided insects with at least sufficient intelligence to prevent them from flying into the flame of a candle, our answer would be: most certainly; only she did not know that men would make candles and light them, and _natura nihil agit frustra_. Insect intelligence is therefore only insufficient where the surroundings are artificial.[237] [235] That the lowest place should be given to the rodents, seems however to proceed from _à priori_ rather than from _à posteriori_ considerations: that is to say, from the circumstance, that their brain has extremely faint or small convolutions; so that too much weight may have been given to this point. In sheep and calves the convolutions are numerous and deep, yet how is it with their intelligence? The mechanical instincts of the beaver are again greatly assisted by its understanding, and even rabbits show remarkable intelligence (see Leroy's beautiful work: "Lettres Philosophiques sur l'Intelligence des Animaux," lettre 3, p. 149). Even rats give proof of quite uncommon intelligence, of which some remarkable instances may be found in the "Quarterly Review," No. 201, Jan.-March, 1857, in a special article entitled "Rats."