Similar diversities in intellectual endowment are apparent when we survey the animal king dom at large. Intelligence appears utterly wanting in numerous and extensive classes, and it varies conspicuously in the members of every tribe among which it is apparent. In his in tellectual powers man is not less eminently raised above all the other beings of creation than in his moral constitution he alone takes note of the phenomena that pass around him with ulterior views, and he alone perceives the relation between effect and cause, preparing and foreseeing consequences long before they happen.
Locomotion is a function so evidently in re lation with the circumstances surrounded by which animals exist, and with the apparatus by which it is accomplished, that it is enough to refer back to the structure for proof and illustra tion of its infinite modifications among the various genera and species of the animal king dom. Some, by their constitution, are inca pable of motion from place to place, but they still perform those partial motions which their preservation as individuals require—taking their food, respiring, voiding their excretions, &c. Those that can move from one place to another have organs in relation to the mode in which this motion is accomplished, whether it be by creeping, by swimming, by running, leaping, flying, &c. &c. Every partial movement ex ecuted by the higher animals has, farther, its own special apparatus : the intestinal canal has its muscular parietes ; the necessity that is felt to communicate internal sensations and ideas has its pathognomonic means in the looks, gestures, sounds of the voice, and so on.
Nor is it only in the greater or less degree of complexity of their general structure, in the num ber and diversity of their particular organs, or in those of the actions whose sum constitutes their vitality,that animals differ from one another; they vary farther in the degree in which these organs and these functions are enchained or mutually dependent. In the most simple animals so complete is the independence of the several parts, that their bodies may be divided into numerous pieces without injury to the vitality of any one of them, each possessing in itself the capacity to commence a separate existence. In animals somewhat more elevated in the scale we observe very extensive powers of reproduc tion at least, of parts that have been lost, and even of continuing existence in very insignificant remainders of their bodies. In the most ele
vated tribes, however, the dependence of every part upon the whole becomes such that neither will the body essentially mutilated survive, nor will any part of the slightest consequence con tinue to live. Among the beings at the bottom of the scale we have in fact found the organiza tion to be homogeneous, or without distinction of parts, and nutrition to be accomplished by means of an immediate absorption and exhala tion; and as every part possesses the structure which makes it capable of these two acts, every part, it is evident, suffices for its own existence. In the higher classes of animal existence, how ever, nutrition requires the concurrence of a mul titude of peculiar acts; and in order that life may be continued in any fragment of one of the mem bers of these, it is plain that this fragment must contain the organs of every one of the functions essential to nutrition. Further, it is certain that the nervous system, when once it has fairly made its appearance, strictly dominates the nutritive function, and that every part of the nervous system itself becomes progressively more and more dependent on one of its portions, the encephalon or brain, as animals stand higher in the scale of creation, and as the functions over which the nervous parts preside respectively are themselves of a higher order. These are. new and additional reasons for the centraliza tion of life, or for the complete dependence of the organs and their functions one upon another among the more perfect animals—man, the quadrumans and quadrupeds, birds, &c.
So much for the acts that minister to the preservation of the individual. Let us now turn to the interesting series by which species are continued. In the very lowest grades this end is accomplished without the concurrence of sexes : at a determinate period of its life the animal either separates into several fragments, which become so many new and independent individuals, or it throws out a number of buds or germs from its external surface or from a particular internal cavity. The first of these modes of reproduction is entitled fissiparous, the second external gemmiparous, and the third internal gentmiparous.