globator; the latter remaining in this initial stage, as an animalcule, through its whole existence; while the former is developed out of it, by successive stages, into a quadruped, or even into a man. Similar functions are performed in different animals by very different organs, the gills of fishes performing the same office as the lungs of the mammalia; and these different organs sometimes exist, at different periods, according to the degree of development, in the same animal. Thus, the tadpole, so long as it continues to be a fish, breathes by gills, which disappear and give place to lungs when it becomes a frog. Similar transformations of the insect tribe are familiar to all. Imperfect or rudimentary organs are found in certain animals, as the mammæ of a man; a particular organ being here developed to a certain extent, though it is not needed; but being developed a little further, it becomes useful in the next set of animals in the scale. The same peculiarity is found among plants; the skilful gardener being able actually to develope these rudimentary organs by supplying the requisite conditions, and thus, as it were, to raise the plant one step in the scale.

Usually, it is true, each species produces only its like,—"every creeping thing and beast of the earth" bringing forth young "after his kind." But the development of a single animal, under the ordinary law, takes place in a few weeks or days; while the development of distinct races and species is the work of a whole creation, and is spread over countless ages. It is reasonable to suppose, that the latter is effected by means of a higher law, manifesting itself only at long intervals. Its infrequent manifestation is no argument against the regularity and necessity of its occurrence,—against its being a law at all. The comet that visits our system only once in five hundred years is controlled by the same inflexible principle which causes the return of another comet once in five years. The conditions requisite for a development more perfect than usual,—that is, for the production of a new species,—instead of a new individual of the same species, may be fulfilled only at long intervals; but when they are fulfilled, the result—the more perfect development—takes place as necessarily, as much by the virtue of law, as the more ordinary phenomenon of the propagation of one race. These conditions may be answered in the successive stages of improvement, through which the earth and its atmosphere pass, during the vast periods of time contemplated in geology. In the era of the old red sand-stone, for instance, there were no higher animals than fishes, because the atmosphere was highly charged with carbonic acid, and could not support respiration by lungs. When the air became purer, the gills were changed into the imperfect lungs of the amphibious tribes, such as the huge saurians and the frogs. Deprive these latter animals, in their lower stage, of all access to the light, and they will not advance to their higher stage. Put a tadpole into a perforated box, and sink it to the bottom of a river, and the animal will never be perfected into a frog; he will grow to an enormous size, but he will continue a tadpole.

We see, then, the process of an "organic creation by law," or by virtue of the inherent qualities of inorganic matter. The ordinary chemical affinities of different substances may draw them together into such compounds as albumen and fibrin, which are the proximate principles of organic tissues. The action of electricity, heat, light, or some other mysterious imponderable agent, on these proximate principles, may produce globules, or germinal vesicles. These germs, multiplying themselves by fissiparous generation, will constitute a stock of animals of a low type, such as a tribe of infusory animalcules. Then "this simplest and most primitive type, under a law to which that of like production is subordinate, gives birth to the type next above it, this again produces the next higher, and so on to the very highest, the stages of advance being in all cases very small,—namely, from one species only to another; so that the phenomenon has always been of a simple and modest character." Thus, the first reptile was born from a fish, the first bird was generated by a reptile, and the first mammifer had birds for its parents. The transformations appear rather astounding, as we pass from one class to another; but the difference between the species, even, is often so great, that the transition appears hardly less difficult. In what quadruped, for instance, do we find the first ancestor of the huge and sagacious elephant? What humble lizard gave birth to those monsters of the fossil world, the plesiosaurus and megalosaurus,