disease, and not from the above acquired habit. He, however, supports Mr. Crotch's statements as to the number and kinds of predacious birds and mammals which, as enemies, devour the Lemmings wholesale, and also that, by a perversion of taste or otherwise, both domestic cattle and Reindeer destroy them. Their occasional enormous increase in numbers our Scandinavian field-naturalist holds is owing to periodic prolific years, to the facility of rearing their young, and to their remarkably easy procreative faculty. Parallel instances among other groups of animals—for instance, unusual swarms of butterflies, locusts, &c.—are well known, though as to the true reason of such departures in number, &c., much that is averred is only conjectural. Coincident with the notable years of the Lemming's migrations, the increase above the normal numbers of rats, mice, shrews, and even the grouse tribe, have been recorded. Mr. Collett affirms that the Lemmings travel chiefly in the direction of the valleys, and not constantly due west, as has been asserted: their great movements en masse are chiefly nocturnal. He is inclined to question Mr. Crotch's theory of a hereditary search for a lost "miocene Atlantis," and is rather of opinion that, in accounting for the periodical excess of multiplication and migratory impulse, a physiological necessity impels them; the nature of this is at present beyond our power to explain rationally and with certainty.
A further contribution to the Natural History of Swine, by Professor Rolleston, was read in abstract, this paper forming an appendix to that previously brought under the notice of the Society. The additional information is in the main confirmatory of the views already expressed by the author; but several important facts,—to wit, relative to the striping of the young of Sus celebensis and S. verrucosus, according to Dr. A.B. Meyer,—with information from other naturalists on kindred points, necessarily cause a modification of the conclusions formerly drawn.
The following botanical papers were read or referred to in abstract:—"On a Collection of Ferns made by Miss Gilpin in the Interior of Madagascar," by Mr. J.G. Baker. "Freshwater Algæ of the Cape of Good Hope," by Prof. Reinsch. "On South-African Liverworts (Hepaticæ)," by Mr. W. Mitten. "On some New Irish Lichens," by the Rev. W.A. Leighton.
April 19, 1877.—George Bentham, Esq., F.R.S., in the chair.
A paper was read by Dr. Francis Day, "On the Geographical Distribution of Indian Fresh-water Fishes" (Part II. The Siluridæ). These, the so-called Sheat-fishes, form a large family amongst the Physostomi of Asia. Mostly scaleless, their mouths are provided with sensitive feelers, which, serving as organs of touch, assist them when seeking for their prey in turbid waters. Vision in such localities would be but of slight service, and, as might be anticipated, their eyes are comparatively small, whilst with advancing age these organs become atrophied, or at least do not increase in the same ratio
