on the latter head are of peculiar interest, inasmuch as it was owing to them that Mr. Darwin was first led to entertain the idea of evolution. As displaying the dawn of this idea in his mind we may quote a passage or two from his Voyage of a Naturalist, where these observations relating to distribution are given :

"These mountains (the Andes) have existed as a great barrier since the present races of animals have appeared, and therefore, unless we suppose the same species to have been created in two different places, we ought not to expect any closer similarity between the organic beings on the opposite sides of the Andes, than on the opposite shores of the ocean."

"The natural history of these islands (of the Galapagos Archipelago) is eminently curious, and well deserves attention. Most of the organic productions are aboriginal creations, found nowhere else; there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean between 500 and 600 miles in width. The Archipelago is a little world within itself, or rather a

satellite attached to America, whence it has derived a few stray colonists, and has received the general character of its indigenous productions. Considering the small size of the islands, we feel astonished at the number of their aboriginal beings, and at their confined range. Seeing every height crowned with its crater, and the boundaries of most of the lava-streams still distinct, we are led to believe that within a period, geologically recent, the unbroken ocean was here spread out. Hence, both in space

and time, we seem to be brought somewhat near to that fact that mystery of mysteries-the first appearance of new beings on this earth."

Next in order of time we have to notice the

Monograph of the Cirripedia. This immensely elaborate work was published by the Ray Society in two volumes, comprising together over 1,000 large octavo pages, and 40 plates. These massive books (which were respectively published in 1851 and 1854) convey the results of several years of devoted inquiry, and are particularly interesting, not only on account of the intrinsic value of the work, but also because they show that Mr. Darwin's powers of research were not less remarkable in the direction

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of purely anatomical investigation than they were in that of physiological experiment and philosophical generalisation. No one can even glance through this memoir without perceiving that if it had stood alone it would have placed its author in the very first rank as a morphological investigator. The prodigious number and minute accuracy of his dissections, the exhaustive detail with which he worked out every branch of his subject-sparing no pains in procuring every species that it was possible to procure, in collecting all the known facts relating to the geographical and geological distribution of the group, in tracing the complicated history of metamorphoses presented by the individuals of the sundry species, in disentangling the problem of the homologies of these perplexing animals, &c.all combine to show that had Mr. Darwin chosen to devote himself to a life of purely morphological work, his name would probably have been second to none in that department of biology. We have to thank his native sagacity that such was not his choice. Valuable as without any question are the results of the great anatomical research which we are considering, we cannot peruse these thousand

pages of closely-written detail without feeling that, for a man of Mr. Darwin's exceptional powers, even such results are too dearly bought by the expenditure of time required for obtaining them. We cannot, indeed, be sorry that he engaged upon and completed this solid piece of morphological work, because it now stands as a monument to his great ability in this direction of inquiry; but at the same time we feel sincerely glad that the conspicuous success which attended the exercise of such ability in this instance did not betray him into other undertakings of the same kind. Such undertakings may suitably be left to establish the fame of great though lesser men; it would have been a calamity in the history of our race if Charles Darwin had been tempted by his own ability to become a comparative anatomist.

But as we have said—and we repeat it lest there should be any possibility of mistaking what we mean the results which attended this laborious inquiry were of the highest importance to comparative anatomy, and of the highest interest to comparative anatomists. The limits of this article do not admit of our giving a summary of these results,

so we shall only allude to the one which is most important. This is the discovery of the "Complemental Males." The manner in which this discovery was made in its entirety is of interest, as showing the importance of remembering apparently insignificant observations which may happen to be incidentally made during the progress of a research. For Mr. Darwin writes:

"When first dissecting Scalpellum vulgare, I was surprised at the almost constant presence of one or more very minute parasites, on the margins of both scuta, close to the umbones. I carelessly dissected one or two specimens, and concluded that they belonged to some new class or order amongst the Articulata, but did not at the time even conjecture that they were Cirripedes. Many months afterwards, when I had seen in Ibla that an hermaphrodite could have a complemental male, I remembered that I had been surprised at the small size of the vesiculæ seminales in the hermaphrodite S. vulgare, so that I resolved to look with care at these parasites; on doing so I now discovered that they were Cirripedes, for I found that they adhered by cement, and were furnished.