"Nil ideo quoniam natum est in corpore, ut uti Possemus; sed, quod natum est, id procreat usum."[224] [224] This is expanded, vol. iv. pp. 825-843. Only this assumption does not explain how, collectively, the quite different parts of an animal's organism so exactly correspond to its way of life; how no organ interferes with another, each rather assisting the others and none remaining unemployed; also that no subordinate organ would be better suited to another mode of existence, while the life which the animal really leads is determined by the principal organs alone, but, on the contrary, each part of the animal not only corresponds to every other part, but also to its mode of life: its claws, for instance, are invariably adapted for seizing the prey which its teeth are suited to tear and break, and its intestinal canal to digest: its limbs are constructed to convey it where that prey is to be found, and no organ ever remains unemployed. The ant-bear, for instance, is not only armed with long claws on its fore-feet, in order to break into the nests of the white ant, but also with a prolonged cylindrical muzzle, in order to penetrate into them, with a small mouth and a long, threadlike tongue, covered with a glutinous slime, which it inserts into the white ants' nests and then withdraws covered with the insects that adhere to it: on the other hand it has no teeth, because it does not want them. Who can fail to see that the ant-bear's form stands in the same relation to the white ants, as an act of the will to its motive? The contradiction between the powerful fore-feet and long, strong, curved claws of the ant-bear and its complete lack of teeth, is at the same time so extraordinary, that if the earth ever undergoes a fresh transformation, the newly arising race of rational beings will find it an insoluble enigma, if white ants are unknown to them. The necks of birds, as of quadrupeds, are generally as long as their legs, to enable them to reach down to the ground where they pick up their food; but those of aquatic birds are often a good deal longer, because they have to fetch up their nourishment from under the water while swimming.[225] Moor-fowl have exceedingly long legs, to enable them to wade without drowning or wetting their bodies, and a correspondingly long neck and beak, this last being more or less strong, according to the things (reptiles, fishes or worms) which have to be crushed; and the intestines of these animals are invariably adapted likewise to this end. On the other hand, moor-fowl are provided neither with talons, like birds of prey, nor with web-feet, like ducks: for the _lex parsimoniæ naturæ_ admits of no superfluous organ. Now, it is precisely this very law, added to the circumstance, that no organ required for its mode of life is ever wanting in any animal, and that all, even the most heterogeneous, harmonize together and are, as it were, calculated