280 



HARDWICKE'S SCIENCE-GOSSIP. 



[Dec. 1, 1870. 



much change, especially if they have been long 

 mounted, that tbey will be almost valueless for accu- 

 rate determination. A communication on this sub- 

 ject appeared in the Pharmaceutical Journal of the 

 19th of November, to which we refer our readers. 



Scale of Snig Eel (Anguilla mediorostris). — 

 The scale now figured should be compared with the 

 scale of eel given in our last volume, on page 187. 

 Although drawn nearly of the same size, the present 

 is a smaller scale, rather more sigmoid than lozenge- 

 shaped, rounded at the ends more than in the com- 

 mon eel, and the cells are spread over the surface, 

 and not concentrically arranged in bauds. The 

 differences in these two scales are so distinct and 

 interesting that both should be found in every cabi- 

 net. It is singular also that, as Mr. Crouch observes, 

 " there are not known any certain external charac- 

 ters by which, this eel may be definitely distin- 

 guished from others ; it therefore becomes a ques- 



The 



are :- 



species enumerated in " British Fishes " 



Fig. 222. Scale of Snig Eel (Anguilla mediorostris) . 



tion how far the difference between them in the 

 processes of the vertebra;, and their entire absence 

 in this species on the first five of these bones from 

 the head, can be relied on as furnishing a sure and 

 constant mark of its distinction from the others." 



Sharp-nosed Eel {Anguilla acutirostris) . 



Dublin Eel (Anguilla Hibernica). 



Broad-nosed Eel (Anguilla talirostris). 



Snig Eel (Anguilla mediorostris). 



Grigg (Anguilla ? ) . 

 The last is an obscure species, or supposed species ; 

 but of the others we should be glad to receive por- 

 tions of skin, with the scales in situ, of the Dublin 

 Eel and the Broad-nosed Eel. The latter is com- 

 mon enough, and the former is found in the Liffey. 

 When these scales are figured, we shall be able to 

 judge whether the microscope cannot aid in separa- 

 ting the Snig Eel, as a distinct and good species, 

 from the rest. 



Opaque Objects. — In the Science-Gossip of 

 Eebruary, 1868, is suggested a way of mounting 

 opaque objects in turned wooden cells with move- 

 able covers ; these cells are not very easily 

 cemented on the slides, and are also clumsy in ap- 

 pearance. Since the above date I have been com- 

 pelled to collect, from time to time, objects mounted 

 in permanently-closed cells, and most of these are 

 now, of course, nearly or quite spoiled. The fixed 

 glass covers reduce the light slightly, injure greatly 

 the definition, and almost invariably become in- 

 crusted ou the under surface by amass of crystallized 

 or granular matter, which becoming with time more 

 and more dense, ends in destroying the slide, by 

 rendering the object practically invisible. The only 

 explanation I can give of the persistence of object- 

 preparcrs in using this form of mounting for dry 

 opaque objects, is that purchasers see the objects 

 when fresh mounted and clean ; add them to their 

 collections ; exhibit them perhaps a few times, and 

 never look at them again. I feel convinced that those 

 microscopists who take the trouble to examine the 

 state of their opaque objects will be inclined to protest 

 against the intolerable nuisance of cemented glass 

 covers. I have now, after many experiments, pro- 

 cured paper pill-box cells, made expressly for the 

 purpose, which I think possess all the requisite 

 qualities. They are inexpensive and neat ; they can 

 be cut down to any required depth ; they are easily 

 cemented on the glass slides with common paste ; 

 they will not fly off on a fall or sudden jar like the 

 ordinary cells ; and when properly adapted they will 

 permit the object to be viewed with high powers 

 and with every kind of illumination. These cells 

 can be now obtained of the makers, Lynch and Co., 

 171 a, Aldersgate-street, and of Mr. C. Baker, the 

 well-known optician of High Holborn. — H. C. 

 Richter, Kensington. 



[It has been suggested that these cells would be 

 improved by the addition of a glass cover, and wc 

 are glad to learn that Mr. Baker proposes to make 

 this improvement. — Ed. S. G.] 



