HARDWICKE'S SCIENCE-GOSSIP. 



69 



second bottle he found " a vigorous specimen," of 

 which he told me that he had had " capital protracted 

 observation." He then mentioned to me that Mr. 

 Lord had sent him specimens last May which were 

 indistinguishable from JV. scapha ; and he considered 

 my species also to be the same. The general aspect 

 of my specimens certainly agreed better with Mr. 

 Lord's figures than with Mr. Gosse's ; but I do not 

 understand Mr. Lord's suggestion, that N. scapha 

 might have been named from a dead specimen ; 

 surely it is clear that Mr. Gosse's first figure was 

 drawn from life. I did not find that the broad out- 

 line was constant in dead specimens, and on the other 

 hand I did find that the breadth of living examples 

 varied considerably. The length, both absolute and 

 relative, of the occipital spines also varies. I saw 

 one specimen in which they were all unequal ; that is 

 to say, they were not arranged in pairs, but each spine 

 differed perceptibly in length from all the others. Most 

 of my specimens came from a puddle at the foot of a 

 coal heap, near a disused colliery. This puddle con- 

 taineda number of lobster-pots, sardine-boxes, and old 

 boots, and other refuse of the same kind. A quantity of 

 floccose vegetation floated on the top ; and in the 

 little heaps formed by this weed the Notholca found 

 its food, which consisted chiefly, I think, of small 

 diatoms. The action of the jaws in a healthy speci- 

 men is remarkably energetic. My experience un- 

 fortunately agrees with Mr. Lord's as to the short 

 life of the species in captivity. It is curious that on 

 the nineteenth of September last I found what I 

 believe to be the same species in a 'shallow and rather 

 muddy stream near here. I then found only two 

 specimens, and have not been able to find any there 

 since. My only reason for doubting the identity of 

 this species is that I sometimes thought I saw a short, 

 slender spine projecting from one side. But this 

 spine, if it existed, was very much shorter than in 

 Mr. Hood"s figure of N. spinifera ; and I never saw 

 more than one spine at a time. The animals were 

 too restless for satisfactory examination. — J. W. 

 Blagg, Greenhill, Cheadlc, Staffordshire. 



Mounting Perishable Crystals Sections. — 

 A mounting medium should be transparent and 

 colourless, if possible, of an index of refraction having 

 reference to the subject treated, and free from mois- 

 ture. It must not be a solvent of the matters that it 

 is employed to preserve. As media of this kind 

 especially worthy of attention for mounting perishable 

 crystals, or such as lose their polish or become opaque 

 in Canada balsam, as well as in the air, Professor 

 Johnstone of Johns Hopkins University, recommends 

 the following: — (1) Finest gum copal dissolved in 

 chemically pure absolute alcohol ; (2) Finest copal dis- 

 solved in chemically pure absolute alcohol ; (3) Dam- 

 mar resin dissolved in rectified spirits of turpentine. 

 No heat should be used in making these solutions, 

 and the resultant liquid should be very thick ; (4) 



Dammar resin dissolved in well-boiled balsam 

 copaiba ; (5) Boiled Chian turpentine dissolved in 

 boiled balsam copaiba ; (6) Dammar resin boiled until 

 the rising scum becomes nearly dissipated, the remain- 

 ing scum to be removed with a spoon. 



Section-Cutting.— The application of the terms 

 "hard " and "soft" paraffin, as employed by W. B. H., 

 is likely to be a little misleading, especially as the 

 majority of microtomists are familiar with medical 

 literature. The term " soft paraffin," or Paraffinum 

 molle, is technically and officially applied in the 

 "British Pharmacopoeia," and consequently in all 

 works of Materia Medica, to a paraffin of a far 

 lower melting-point than that so designated by your 

 correspondent. It is the body popularly known as 

 Vaseline. A paraffin imbedding wax of any desired 

 melting-point below that of hard paraffin could 

 readily be prepared, by melting together varying 

 proportions of the official " Paraffinum durum " and 

 " Paraffinum molle." These could readily be obtained 

 from any pharmacist. — J. Oldham Braithivaite. 



Pond Dredging and Collecting. — In reply 

 to your correspondent's query in the Science-Gossip 

 for February [p. 45] as to the net to be used in 

 collecting Rotifera, &c, I should advise him not to 

 use a net at all. The best appliance with which I 

 am acquainted is made by fastening a wide-mouthed 

 glass bottle (such as a pomatum pot) to the end of a 

 walking-stick, by means of a stout copper wire, 

 which should be tightly whipped with strong thread 

 and varnished. For more delicate work or for 

 use in ponds, &c, comparatively free from weeds, 

 a large sized test-tube might be substituted for the 

 bottle and should be fastened to a short thin length 

 of bamboo as follows : — Take a six-inch length of 

 caoutchouc tubing, and make a cross cut three- 

 quarters through, at about an inch from one end : 

 then another at right angles to the first along the 

 other five inches : the result is a short piece of tube 

 with a five-inch slip of gutta-percha. The tube is 

 slipped over the end of the rod, and the free end of 

 the flap is pushed between the rod and the tubing, 

 the test tube placed in the loop so formed and the slip 

 drawn tight and fastened off. — Jno. Eyre. 



ZOOLOGY. 



The Lesser White-Fronted Goose {Anser 

 erythropas, Linn.). — A goose identified as one of this 

 species, and apparently a wild one, was shot near 

 this town in January last. This bird not having been 

 admitted into the British list, the capture is an 

 interesting one, and I shall be pleased to give further 

 information on the subject to any one who will apply 

 tome. — W. Gyngell, Wellington, Somerset. 



