Abstract
Two forms of considerable interest belonging to this group were found to be tolerably abundant. They belong to the genera
Tetrastemma
and
Geoplana
, I can scarcely entertain a doubt that these animals will finally prove to have a much wider geographical range, or, in other words, that it would be premature to regard them as peculiar to the island of Rodriguez. I may also express it as my belief, that the Land Planarians are much more numerous than has been supposed hitherto; but, unfortunately, with but few exceptions, Zoologists who have visited this region, have paid but little attention to them. The species of
Tetrastemma
is, I believe, the third Land Nemertean which has been discovered, one having been found by Semper in the Pelew Islands, and another quite recently by the late Dr. Von Willemoes Sulim in the Bermudas, which he has described in “Annals and Magazine of Natural History,” 1873, xiii., p. 309. He expresses it there as his opinion that land Nemerteans are much more common on tropical islands than has commonly been supposed, and the discovery of one at Rodriguez goes a long way towards justifying his supposition. Dr. Suhm’s, like mine, is a species of
Tetrastemma
(
T. agricola
), but the present species is much more truly a terrestrial species than his, inasmuch as it occurs in woods—in damp rotten wood—and similar situations. This was the case also with that discovered by Semper. The animal was killed almost immediately by immersion in salt-water, for which it showed its distaste by rapidly exserting its proboscis, as it does when placed in alcohol. Fresh water, on the contrary, was by no means so distasteful to the animal, and I have had them remain alive for a whole night in it. It never, however, was observed to attempt to crawl on the upper surface of the water, though it would ascend the sides of the glass, and, if possible, settle itself outside the water. All the specimens seemed to be exceedingly torpid, and showed no disposition to move. If disturbed in their lodgment in rotten wood they appeared to shrink away into some recess, but never attempted to move for any length of time. It would seem to be very probable that this season was one of torpidity with them.