Science-gossip . w I20 SCIENCE GOSSIP. moss {Fontinalis antipyretica), which is oftenstudded with Mellcerta and Floscules, and thestoneworts CJiara and Nitella. Mr. Scherren saysthe water-violet {Hottonia palustris) should not h&admitted, as it is not a free grower, and decaysrapidly. The animal life must, of course, be leftto the individual collector; hydi-as, vorticellae,the tube-building rotifers, etc., seem to requirelittle or no attention other than the supply of foodin the shape of Infusoria. The Polyzoa, on theother hand, require shading from direct light, andare best kept in a jar prov
Science-gossip . w I20 SCIENCE GOSSIP. moss {Fontinalis antipyretica), which is oftenstudded with Mellcerta and Floscules, and thestoneworts CJiara and Nitella. Mr. Scherren saysthe water-violet {Hottonia palustris) should not h&admitted, as it is not a free grower, and decaysrapidly. The animal life must, of course, be leftto the individual collector; hydi-as, vorticellae,the tube-building rotifers, etc., seem to requirelittle or no attention other than the supply of foodin the shape of Infusoria. The Polyzoa, on theother hand, require shading from direct light, andare best kept in a jar provided with weed. Thefree-swimming Eotifers must also be kept insmall jars or bottles, and fed with the expressedjuices of aquatic vegetation or they will be is difficult to keep Yolvox for more than a weekor so. MAKIXC4 DEXDEiTES.^If anyone ^isiting theSouth Kensington Natural History Museum ?«ill gointo the Mineral Gallery, and look into the firstcase by the left-hand wall, he will see there on two. * ^ ^« J^ fc,.,> C^-\H [Figs. 1 axd 2. Artificial Dexdrites, slabs of limestone, each about 6 inches square, twobeautiful fern-like pictures imprinted. So clearand regular are they, and so apparently imbeddedin the stone, that an unscientific observer would be inclined to assert that they- are -fossil ferns,,which would be quite an excusable mistake, seeingthat they have the carbonaceous appearance offerns as seen in coal shales. Nevertheless thefigures are purely mineral productions formed bymechanical means, as will be seen by anyone who-chooses to follow out the simple experiment whichfurnished the materials for the accompanying illus-trations (figs. 1 and 2). The black matter, formingthe dendrites on the slabs, is manganese, which ina plastic state penetrated a fissure m a rock, andon the fissure slowly widening, by one of those-earth movements which are always in progress,the plastic matter ran out over each face of thefissure in the fern-like form there seen. Dend
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