ages with which this Theory has made us familiar. Thus the process had to be hastened, for when the adaptation had been once effected,' a facility of change hastened the process of mutation, and the winged tribes found comparatively little difficulty in producing new orders and families, as circumstances seemed to encourage the 'plastic tendencies' of their organizations.

But though Natural Selection was thus accelerating matters for the emergency, the other principle, extermination, was by no means dormant, for we are informed that 'extinction has played an important part in defining and widening the intervals between the several groups in each class. We may thus account even for the distinctness of whole classes from each other-for instance, of birds from all other vertebrate animals-by the belief that many unusual forms of life have been utterly lost, through which the early progenitors of the birds were formerly connected with the early progenitors of the other vertebrate classes' (463).

Thus, by the process of believing' as a substitute for proof, we are to understand that such was the process. Many unusual forms' in the progress of bird-making have been utterly lost: these forms must indeed have been by myriads to account for the distinction at last effected, when, 'in a long succession of ages,' the real bird was at last produced, to say nothing of the countless experiments lost in connecting the various orders and species of birds. All these unusual forms, exterminated in the Struggle for Life, have disappeared, and can nowhere be found, and so it is that we see the bird separated from all vertebrated animals by an apparently vast chasm, and all the families of birds separated from one another. This

feriori as be us a liable manner, peroned or so is the mare mazerica with exists heWhen the vive da in nizil and its destinies

Frey organized bemg," says he, forms a while, an unique and periert gym the parts of which mutually correspond, and more in the same definitive action by a reciprocal reactice. Now offer parta ean change writinut the whole changing, and consequently each of them, separately considered, points cut and marks all the others. Thus, if the intestines of an animal are so organized as only to digest flesh, and that in a fresh state, it follows that its jaws must be constructed to devour prey, its claws to seize and tear it, its teeth to cut and divide it; the whole structure of the organs of motion such as to pursue and catch it ; its perceptive organs to discern it at a distance: Nature must even have placed in the brain the necessary instincts to know how to conceal itself and lay snares for its victims. That the jaw may be enabled to seize it must have a cer

tain-shaped prominence for the articulation, a certain relation between the position of the resisting power and that of the strength employed with the fulcrum; a certain volume in the temporal muscle, requiring an equivalent extent in the hollow which receives it, and a certain conyexity of the zygomatic arch under which it passes; this zygomatic arch must also possess a certain strength to give strength to the masseter muscle.

That an animal may carry off his prey a certain strength is requisite in the muscles which raise the head; whence results a determinate formation in the vertebræ or the muscles attached, and in the occiput where they are inserted.

That the teeth may cut the flesh they must be sharp; and they must be more or less so according as they will have, more or less exclusively, flesh to cut. Their roots should be more solid as they have more and larger bones to break. All these circumstances will, in like manner, influence the development of those parts which serve to move the jaw.

'That the claws may seize the prey they must have a certain mobility in the talons, a certain strength in the nails, whence will result determinate formations in all the claws, and the necessary distribution of muscles and tendons it will be necessary that the forearm have a certain facility of turning, whence again will result determinate formation in the bones which compose it; but the bones of the forearm articulating in the shoulder-bone cannot change its structure without this latter also changes.

:

In a word, the formation of the tooth bespeaks the structure of the articulation of the jaw; that of the scapula indicates that of the claws; just as the equation of a curve involves all its properties; and in taking each property separately, as the basis of a particular equation, we should

find again both the ordinary equation and all the other certain properties; so, the claw, the scapula, the articulation of the jaw, the thigh-bone, and all the other bones, separately considered, require the certain tooth, or the tooth requires them reciprocally; and, beginning with any one, he who possessed a knowledge of the laws of organic economy would detect the whole animal.

'We see, for instance, very plainly, that hoofed animals must all be herbivorous, since they have no means of seizing on their prey. We see, also, that having no further use for their forefeet than to support their bodies, they have no occasion for so powerfully-framed a shoulder; whence we may account for the absence of the clavicle and acromion, and the straightness of the scapula. Not having any occasion to turn their foreleg, their radius will be solidly united to their ulna, or, at least, articulated by a hinge-joint, and not by a ball and socket, with the humerus. Their herbaceous diet will require teeth with a broad surface to crush seeds and herbs; this breadth must be irregular, and for this reason the enamel parts must alternate with the osseous parts. This sort of surface compelling horizontal motion, or the grinding of the food to pieces, the articulation of the jaw cannot form a hinge so close as in carnivorous animals: it must be flattened, and correspond with the facing of the temporal bones, more or less flattened. This temporal cavity will only contain a very small muscle,-will be small and shallow.

'We have no difficulty, then, in understanding that an animal is a complete machine, with harmonies and correspondent provisions in every part of its organization: that the whole creature, in the integrity of its being, recognizes its own character, and executes its own will by the concur

rent aid and perfect agreement of every distinct portion of its body that there is nothing empirical in its structure, nothing mutable or fluctuating in its system; and that no change, in the true meaning of change, could take place in any of its parts without impairing the whole, which is perfect in the consentaneous perfection of all its members, directed to one object and operating with one aim, to fulfil the preordained destinies of the animal's life.'

Every animal that exists is, for the purposes of its existence, as perfect as it can be; and is as far out of the reach of ideal improvement, and beneficial changes in a slight degree,' as the sun itself, whose light and heat sustain the existence of every organic being.