[B] Professor Ramsay has since shown that a glacial epoch probably occurred at the time of the Permian formation, which will more satisfactorily account for the comparative poverty of species.

[C] The theory of Natural Selection has now taught us that these are not the steps by which limbs have been formed; and that most rudimentary organs have been produced by abortion, owing to disuse, as explained by Mr. Darwin.

[D] Written at Ternate, February, 1858; and published in the Journal of the Proceedings of the LinnÆan Society for August, 1858.

[E] This is under estimated. The number would really amount to more than two thousand millions!

[F] That is, they will vary, and the variations which tend to adapt them to the wild state, and therefore approximate them to wild animals, will be preserved. Those individuals which do not vary sufficiently will perish.

[G] W. C. Hewitson, Esq., of Oatlands, Walton-on-Thames, author of “Exotic Butterflies” and several other works, illustrated by exquisite coloured figures drawn by himself; and owner of the finest collection of Butterflies in the world.

[H] It has been very pertinently remarked by a friend, that, if young birds did observe the nest they were reared in, they would consider it to be a natural production like the leaves and branches and matted twigs that surrounded it, and could not possibly conclude that their parents had constructed the one and not the other. This may be a valid objection, and, if so, we shall have to depend on the mode of instruction described in the succeeding paragraphs, but the question can only be finally decided by a careful set of experiments.

[I] Mr. Bayma’s work, entitled “The Elements of Molecular Mechanics,” was published in 1866, and has received less attention than it deserves. It is characterised by great lucidity, by logical arrangement, and by comparatively simple geometrical and algebraical demonstrations, so that it may be understood and appreciated with a very moderate knowledge of mathematics. It consists of a series of Propositions, deduced from the known properties of matter; from these are derived a number of Theorems, by whose help the more complicated Problems are solved. Nothing is taken for granted throughout the work, and the only valid mode of escaping from its conclusions is, by either disproving the fundamental Propositions, or by detecting fallacies in the subsequent reasoning.