I20 



SCIENCE' GOSSIP. 



moss {Fontinalis antipyretica), which is often 

 studded with Mellcerta and Floscules, and the 

 stoneworts CJiara and Nitella. Mr. Scherren says 

 the water-violet {Hottonia palustris) should not h& 

 admitted, as it is not a free grower, and decays 

 rapidly. The animal life must, of course, be left 

 to the individual collector; hydi-as, vorticellae, 

 the tube-building rotifers, etc., seem to require 

 little or no attention other than the supply of food 

 in the shape of Infusoria. The Polyzoa, on the 

 other hand, require shading from direct light, and 

 are best kept in a jar provided with weed. The 

 free-swimming Eotifers must also be kept in 

 small jars or bottles, and fed with the expressed 

 juices of aquatic vegetation or they will be lost. 

 It is difficult to keep Yolvox for more than a week 

 or so. 



MAKIXC4 DEXDEiTES.^If anyone ^'isiting the 

 South Kensington Natural History Museum ■«"ill go 

 into the Mineral Gallery, and look into the first 

 case 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, two 

 beautiful fern-like pictures imprinted. So clear 

 and regular are they, and so apparently imbedded 

 in the stone, that an unscientific observer would 



be inclined to assert that they- are -fossil ferns,, 

 which would be quite an excusable mistake, seeing 

 that they have the carbonaceous appearance of 

 ferns as seen in coal shales. Nevertheless the 

 figures are purely mineral productions formed by 

 mechanical means, as will be seen by anyone who- 

 chooses to follow out the simple experiment which 

 furnished the materials for the accompanying illus- 

 trations (figs. 1 and 2). The black matter, forming 

 the dendrites on the slabs, is manganese, which in 

 a plastic state penetrated a fissure m a rock, and 

 on the fissure slowly widening, by one of those- 

 earth movements which are always in progress, 

 the plastic matter ran out over each face of the 

 fissure in the fern-like form there seen. Dendrites- 

 are common in many limestone districts, but of 

 course vavj much in size and distinctness. I have- 

 obtained very fair ones on children's marbles by 

 steeping them in muriatic acid and water, to remove 

 the artificial colouring matter, and then polishing 

 them if they showed any sign of a dark marking 

 on the surface. The dendrites which occur in 

 IDaper are differently produced. (See S.-G., vol. vii.. 

 p. 258.) To produce the dendritic appearance as- 

 seen on rocks let two plane sui'faces {e.g. two 

 panes of glass) be separated by a film of suitable- 

 plastic material such as paste from flour ; let one 

 svn-face be rotated on the other through a small 

 arc, gently lift the top edge of the upper plane- 

 about Jgth of an inch, and the j^lastic matter then, 

 collects into branching forms similar to the struc- 

 ture of dendrites. Sometimes they assume a f ucoid 

 form, at others that of some forms of lichens,, 

 varying vrith the fluidity of the material used. 

 Further experiments would doubtless result in more- 

 beautiful and varied forms. — E. Moor, 49 Arbitra- 

 tion Street, Balhy Road, Boncaster. 



Food of Prehistoric Man. — I have read with 

 much interest the paper on " Food of Prehistoric- 

 Man " in the July issue of Science-Gossip, and 

 regret with Dr. Chartres "\Miite the jDrobable loss of 

 this unique material. There is a possibilit}-, how- 

 ever, of saving a portion of it, and to this end the 

 slides should be put in pah-s, back to back, into a. 

 3-inch by IJ-inch tube half filled with xylol,. 

 until all have been treated. They should remain, 

 until the covers fall off. The covers sho\ild then 

 be carefully rinsed and lifted out of the tube Avithi 

 forceps, and the xj^lol allowed to settle. After de- 

 canting and removing as much as possible of the 

 liqi^id add absolute alcohol, again allowing the 

 contents to settle, and give a second bath of 

 alcohol. The material should remain in this bath 

 for several hom-s, and oan then be transferred to- 

 xylol and mounted in xylol bMsam. This will pre- 

 serve all that has not decomposed while in the 

 original mounting medium, but it is probable that 

 all organic matter is lost. In dealing with fresh 

 material it would be well, after decalcifj'ing in. 

 hydrochloric acid, to remove remaining acid with- 

 distilled water, and, after allowing the pieces of 

 tissue to swell to their original dimensions in this 

 for at most an hour, to transfer it to 70 per cent, 

 alcohol, then to absolute alcohol, and through xylol 

 to the mounting medium. It might be found worth 

 while to fixbiefore putting into the alcohol, if the 

 presence of any soft organic tissue is susjiected. 

 A fixing solution which would probably be found 

 most suitable is made by adding 1 part of 50 per- 

 cent, acetic acid to 20 parts of 1 per cent, cliromic 

 acid. Well wash material in water and dehydi-ate- 

 in alcohol, beginning with -10 per cent. In mount- 



