Cuvier had preceded Lamarck in specifying the kinds and degrees of variation, which his own observations and critical judgment of the reports of others led him to admit.

The laws of Coexistence;-the adaptation of structure to function; and to a certain extent the elucidation of natural affinities may be legitimately founded upon the examination of fully developed species;-But to obtain an insight into the laws of development,-the signification or bedeutung, of the parts of an animal body demands a patient examination of the successive stages of their development, in every group of Animals.

Mr. Darwin refers to the multitude of the individual of every species, which, from one cause or another, perish either before, or soon after attaining maturity.

Homologue. The same organ in different animals under every variety of form and function.

Analogue. A part or organ in one animal which has the same function as another part or organ in a different animal.

The combination of such characters, some, as the sacral ones, altogether peculiar among Reptiles, others borrowed, as it were, from groups now distinct from each other, and all manifested by creatures far surpassing in size the largest of existing reptiles, will, it is presumed, be deemed sufficient ground for establishing a distinct tribe or sub-order of Saurian Reptiles, for which I would propose the name of Dinosauria.

No naturalist has devoted more painstaking attention to the structure of the barnacles than Mr. Darwin.