During the visit which the Archduke Ferdinand paid, in 1819, to the Magdalena Grotto, the most remarkable parts of the cave were brilliantly illuminated, so as to produce a magical effect. Charon’s boat, issuing from a dark recess, came gliding along over the black surface of the pool. The grim ferryman drew up his net before the august visitors, and presented them with six Protei that had been entangled in its meshes. Dr. Schmidl mentions part of the subterranean river in the Planina Cave, 1,715 fathoms from the entrance, as the spot where the Protei are most abundant. Near to a small cascade which the rivulet here forms over a reef, the waters absolutely swarm with them, and the light-coloured animals, darting about in all directions in the dark stream, afford a strange and picturesque spectacle. As the cavern is of most difficult access, they here enjoy a tranquillity rarely disturbed, and no doubt they have many other still more hidden retreats, to which man is incapable of penetrating. The best method for transporting the Proteus is now perfectly understood, and living specimens have been conveyed as far as Russia, Hungary, and Scotland. All that they need is a frequent supply of fresh water, and a careful removal of all light. Their food need cause no trouble, as the water contains all they require. It is recommended to lay a piece of stalactite from their native grotto in the vase in which they are transported. When resting or sleeping, they then coil themselves round the stone, as if tenderly embracing it. In this manner they have already been kept above five years out of their caverns. The guides to the Grotto of Adelsberg have always got a supply on hand, and sell them for about two florins a-piece. On turning our attention from the grottoes of Carniola to those of the New World, we find, in the vast Mammoth Cave in Kentucky, a no less interesting animal creation, which, though different from that of the Austrian caverns, still shows a certain family resemblance, and affords another proof that a similarity of external circumstances always produces analogous forms of organic life. Thus, the two blind beetles which are found in the Mammoth Cave belong to the same genera (_Anophthalmus_ and _Adelops_) that have also their representatives in the Grotto of Adelsberg. The largest insect is here a species of cricket, with enormously long antennæ; there are also two small white eyeless spiders and a few crustaceans. The Mammoth Cave has no proteiform reptile to boast of, but a peculiar blind rat and a peculiar blind fish.