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The Migration of Eels.—During a conversation upon the habits of certain fish, my informant mentioned that on the top of a cotton mill, owned by a friend of his, was a large water-tank, and at the bottom another. These were always kept filled with water for the purposes of the factory. The tank at the top requiring to be cleansed, was emptied, when, lo, a number of eels were found in it. How did they get there? None could tell. In the lower tank they were always kept, but not in the upper. However some time afterwards the mystery was solved. The walls were wet on one side, from a leakage in the upper tank, and up these moist places eels were observed wriggling from the bottom vessel, until they attained the top of the lofty building, when they precipitated themselves into the upper tank.—Charles Strange.

The Sand-Launce, the Herring, and the Smelt (Ammodyes lancea, Clupea Harengus, and Osmerus eperlanus).—Mr. P. H. Gosse, at page 113 of his recently-published book, "A Year at the Shore," says that he can vouch for the Sand-Launce "making a very attractive tenant of an aquarium, where it will live a considerable time." I am glad to hear this, because, with the tolerably complete arrangements of the Hamburg Aquarium, I have been unable to get it to live for more than a few minutes, or an hour or so, or, in one instance, in a perfectly dark and very shallow stream of water, and running strongly, for a day and a half. I have tried on several occasions, the last time being a fortnight ago, when I received from Heligoland twenty nice specimens, in an eight-gallon vessel of sea-water. On opening the can, the fish were swimming about in perfect health, apparently, and I thought that if so many lived in that quantity of fluid during a ten-hours' voyage in warm weather, I should have a good chance of preserving them alive when distributed by twos and threes in tanks in perfect condition, and with streams running, and containing from twenty-five to one thousand gallons' capacity each, especially if I took care, as I did, that the temperature and specific gravity of the water in which the fish travelled were exactly the same as in my tanks. But it was all in vain: the creatures took an impetuous rush and a wriggle through the aquaria, and turned up dead, some almost instantly, and some a little later, with the exception of the one I have mentioned, and which lived thirty-six hours. Can any one, therefore, give me actual dates of the times in which Launce has been kept in the aquaria, together with a statement of all the circumstances under which the conservation was managed? Did the Launce eat anything, and if so, what? Did they, or it, burrow in sand in the aquarium? Mine did not; they were too frightened to do anything. So also with Herrings. I have received them cooper up in small quantities of water after they have been a whole day on the journey here, and yet looking as well as fish possibly could look; but on being placed in the aquarium, they shot wildly and aimlessly hither and thither, ploughing the surface of the water into waves with their extreme speed, and sometimes even jumping clean into the air, as if in pain, and then bolting into a corner and dying in a very short time. So also with the Smelt. They, too, have reached me alive and well, but have behaved and died under precisely the same circumstances as the other two fishes named. It is difficult to account for these things by reference to any known law; but all of these three fishes have scales which are removed by a very slight touch, and their bodies of are a peculiar gleaming silvery-blue colour, and they have a quivering or trembling motion of the muscles of their sides, which can be plainly seen through their delicate thin skins; and I have always noticed that when these appearances exist in any fish, it is difficult to be kept in confinement in an aquarium. I should be glad to know why, on anatomical grounds. Can any one please tell me?—W. Alford Lloyd, Zool. Gardens, Hamburg.

On the Management of Ferns in Cases.—Do fern-cases require air? asks a correspondent in Science Gossip for October. Having had some little experience in fern culture, I reply that in my opinion ferns will not thrive in a small case without it. Mr. Ward, I believe, thought that it could be dispensed with in his cases, but I never could get my ferns to thrive unless there were some means for the foul air to escape, and fresh air admitted. All plants, save mosses, require fresh air properly admitted, and even mosses would be better, according to my notions, with a little of it; but they can be cultivated in an air-tight case, provided they are well shaded. Your correspondent Mr. G. Norris also asks respecting the soil proper for fern-cases. What sorts does he intend to grow? Different ferns require different soil. Some thrive in the shade, others on rocks; some in moist places, others in dry. He must imitate their natural soil as well as he can; get peat, turfy loam, and small sandy stones well mixed together, and fill his case with it. The best stand for a case of ferns is facing the morning sun, and the bottom of the case and its glass cover ought to be in two different parts; it is so much nicer for planting and arranging your ferns when this is the case—a door is not half so convenient. You know the glass soon gets covered inside with moisture, and this moisture ought to be evaporated by air; for excess will cause moldiness to appear on the ferns.—Helen Watney.