HARDWICKE'S SCIENCE-GOSSIP. 



S7 



ment, for varying thickness of cover glass, upon 

 objects, is very highly spoken of by leading English 

 observers. If this work without counterbalancing 

 objections, a revolution in the future of objectives 

 may be expected. The object must be somewhat 

 specially mounted. Danger that the fluids may inter- 

 mingle under necessary traversing when a living 

 object in water is examined with a water immersion 

 lens is not \ lessened by oil substituted, and Mr. 

 Dallinger rejoices that high power English dry 

 lenses, usually, suffice for investigation of minutest 

 living things, from the study of which, as he remarks, 

 so much may be anticipated."^ 



Mounting Polyzoa, &c— Mr. Thomas Lisle, of 

 Wolverhampton, gives in the " Midland Naturalist" 

 for March, the following process for mounting these 

 objects: — "Place the polyzoa in a deep cell with 

 some of the pond water ; let them remain undisturbed 

 until they have expanded their tentacles, then 

 suddenly let fall a drop of alcohol into the cell. 

 This kills them instantly. The cell is then filled 

 with distilled water or glycerine, and sealed in the 

 usual way. Rotifers may be treated in the same 

 manner, but the cell may be shallow." 



Cells for Dry Objects. — We have received from 

 Mr. H. P. Aylward, of Manchester, some prepared 

 cells, which we believe may be useful to those who 

 mount many dry objects. They are made, either of 

 paper, or cloth rings, well coated with, we believe, 

 a shellac varnish, which becomes hard and glossy, and 

 when the objects are to be mounted the application of 

 heat melts these rings to the slip and fastens on the 

 thin cover. Their use is of course limited to those 

 objects which will bear heat, but most foraminifera 

 and other calcareous organisms and many microscopic 

 fossils can thus be rapidly mounted, for as soon as the 

 slide is cold the varnish becomes quite hard and there 

 is no danger of the object becoming attached to the 

 edge, which sometimes happens when rings are 

 fastened on with gold size or other varnish. The thin 

 glass when it is being attached should not be touched 

 with a cold needle, or condensation takes place under 

 the point ; but if this is avoided we have found the 

 glass remains quite clear, and the object is in no way 

 obscured. It would seem as if the attachment is 

 likely to remain permanently hard and firm, but that 

 can only be proved by lengthened experience. 



New Species of Rhizopods — In the "American 

 Quarterly Microscopical Journal " for January, 

 Professor W. S. Barnard describes some new kinds 

 of American Rhizopods. As a rule, the American 

 species are of European genera, and it is very seldom 

 a new one is discovered. Our species (Eitglyp/iia 

 tegulifera), appears to be a very interesting form, on 

 account of its peculiar shell. It was found among 

 fresh-water algae near New York. We take advantage 

 of this opportunity to express our high opinion of this 

 well got up and excellently edited journal. 



Removing Air-bubbles.— Mr. F. C. Clarke, in 

 the "American Naturalist," gives the following 

 method as practised by Dr. Johnson : The apparatus 

 he employs is of very simple construction, being a 

 common dentist's vulcaniser, the means — steam. The 

 preparations to be thus treated, especially those of 

 wood, are prepared in the usual way and made ready 

 for mounting. They are next placed in a small 

 vessel of any material which will resist a certain 

 amount of heat. Dr. Johnson uses a small glass 

 phial in his experiments : this is filled up with water 

 after all the specimens (as many as it can conveniently 

 hold) are placed within. A cork can be used, but 

 a slit must be cut in it to allow the escape of air and 

 the admission of steam and hot water. A little water 

 is now poured into the vulcaniser, the bottle of objects 

 placed within, and the lid of the machine screwed 

 down air-tight. The whole is now heated to a 

 temperature of about 300 Fahr. for a few minutes. 

 This temperature is sufficient for all practical purposes. 

 When sufficiently cooled the phial is removed, the 

 water drained from the bottle, and alcohol substituted. 

 The specimens are now ready for mounting. By this 

 process the specimens are made absolutely free from 

 air, for the steam penetrates and forces out the air 

 from the objects operated upon ; and the tissues 

 remain undestroyed. 



ZOOLOGY. 



Planorbis marginatus. — Professor Ralph Tate 

 in his work on " British Mollusks," says, Planorbis 

 marginatus is unknown in Scotland. Perhaps it may 

 interest some of the readers of Science-Gossip to 

 know that I have lately taken upwards of a dozen 

 specimens from Duddingston Lock, Edinburgh. Also 

 specimens of P. carinatus, P. Nautileus, and P. 

 contortus, the last-named species is very numerous. — 

 John Adams. 



The Echinus in Aquaria. — Would any of the 

 readers of Science-Gossip inform me of the cause of 

 the absence of the Echinus in our large aquaria 2 

 Is it that animals found in deep sea dredging, will 

 not flourish in these, or is it a difficulty as regards 

 supplying it with proper food ? I have never succeeded 

 in keeping them in small aquaria for more than 

 a short time j the last brought me on December 7 

 lived for a month, the spines then began to fall off* 

 quickly, and in a day or so it died. The Echinus is 

 such an interesting inhabitant of an aquarium, that I 

 should be very glad to know if it is possible to keep 

 it for any time in captivity. — M. D. 



The Hooded or Royston Crow (.Coi-utts comix). 

 — These noble birds have been numerous in this 

 neighbourhood for some weeks, one or two will 

 occasionally perch on the rails of my garden fence, 



