EDITORIAL GLEANINGS.
In the 'Quarterly Journal of Microscopical Science,' Dr. W.G. Ridewood has published a most valuable paper "On the Structure of the Hairs of Mylodon listai, and other South American Edentata." We are glad to see that Dr. Ridewood is dissatisfied with the present composition of the order Edentata, which, as he remarks, will probably prove to be an unnatural assemblage of animals, and that, acting on further knowledge, it will probably prove necessary to remove the Old World forms Manis and Orycteropus to constitute two new orders by themselves. The diagnoses of hair-structure given in this communication are of too technical a nature for reproduction in our pages; but the publication has prompted a paper by Mr. R. Lydekker in 'Knowledge' on "Plant-bearing Hair," of which we cannot do better than give the following abstract:—
The author remarks that, "apart from its extremely coarse and brittle nature, the most striking peculiarity of the outer hair of the Sloths is its more or less decidedly green tinge.... Now green is a very rare colour among mammals, and there ought therefore to be some special reason for its development in the Sloths. And, as a matter of fact, the means by which this coloration is produced is one of the most marvellous phenomena in the whole animal kingdom—so marvellous, indeed, that it is at first almost impossible to believe that it is true. The object of this peculiar type of coloration is, of course, to assimilate the animal to its leafy surroundings, and thus to render it as inconspicuous as possible; and, when hanging in its usual position from the under side of a bough, its long, coarse, and green-tinged hair is stated to render the Sloth almost indistinguishable from the bunches of grey-green lichens among which it dwells. In the outer sheath of the hairs of the aï there are a number of transverse cracks, and in these cracks grows a primitive type of plant, namely, a one-celled alga. In the moist tropical forests forming the home of the Sloths the algæ in the cracks of their hair grow readily, and thus communicate to the entire coat that general green tint which, as already said, is reported to render them almost indistinguishable from the clusters of lichen among which they hang suspended."
Mr. Lydekker adds some weighty remarks in his paper. "It is quite clear that an alga would have been of no advantage to the Sloths
