452 



SCIENTIFIC NEWS. 



[May II, l8 



more or less flattened. Too coarse was the disturbing 

 influence to interfere with the shells that were — ■ 



" Slight, to be crushed with a tap 

 Of my finger-nail on the sand ; 



Small, but a work divine ; 

 Frail, but of force to withstand, 



Year upon year, the shock 

 Of cataract seas that snap 



The three-decker's oaken spine ..." 

 Having procured specimens of the Foraminifera we may 

 require to examine the shells by transmitted light under 

 the microscope in order to ascertain their structural 

 characters, when thin sections must in most cases be 

 made ; although in a few instances the shell is thin and 

 small enough to allow of high powers being used, as in 

 Uvigerina (fig. 15), which is transparent enough for 

 microscopic examination when mounted in Canada 

 balsam. Again, for some specimens it will not be 

 necessary to cut away more than half the shell, as, 

 for instance, if we wish to examine the arrangement in 

 those forms where the outer chambers embrace the 

 inner ones, as in Miliolina (fig. 5). Where however the 

 shell has to be sliced, we place upon the hot plate of our 

 mounting table, which may consist of a brass plate sup- 

 ported on a tripod beneath which burns a spirit lamp, a 

 piece of glass of the size of half an ordinary microscopic 

 slide, dropping a little balsam on the surface, and heating 

 the glass gently. When the balsam has been warmed to 

 the condition of toughness when cold, a small piece of 

 mica is placed upon the still liquid balsam on the glass 

 plate, pressed down and another drop of balsam placed 

 en the mica. During the heating of this last application 

 of balsam the shells are placed on the mica, when they 

 proceed to sink into the balsam as they are warmed. It 

 is a good plan to have three shells arranged in a 

 triangle on each plate, as this facilitates equal grinding. 

 The object of gradual heating is that the shells 

 may be thoroughly permeated by the balsam, and their 

 chamber-walls consequently protected if they be thin. 

 When the plate thus prepared has cooled, the balsam 

 should be just tough or unimpressible to the finger-nail. 

 Taking an even-textured piece of snakestone — that is, one 

 in which the spots are evenly distributed throughout — 

 a clean cutting surface may be produced upon it by 

 grinding on a piece of plate glass with some emery of a 

 kind slightly coarser than that of " flour." The surface 

 of the stone must of course be thoroughly cleansed from 

 any trace of emery, when the glass slip with the shells 

 should be rubbed upon it very gently at first, with a 

 circular motion, now and again examining them with a 

 lens, until just about half of each shell remains. It will 

 be foMnd that a few rubs on the stone will generally 

 suffice for the ordinary-sized Foraminifera, so that 

 extreme care must be taken throughout the process. 

 Again placing our shp on the hot plate, after having 

 •carefully dried it, we put beside it a mounting slip which 

 we touch in the centre with a little balsam, and allow it 

 to harden down. By the time this latter is prepared we 

 can remove with forceps the mica bearing the shells, 

 with their upper halves ground away, from the first 

 plate, and turning the film over with the shells beneath 

 we let it fall inclined, to exclude air, on to the second 

 slip. When cold the mica may be removed by inserting 

 a knife point under one corner, and the second grinding 

 proceeded with. The sections, after having been ground 

 upon the stone with water until the requisite thinness 

 has been attained, are mounted as transparent objects in 

 balsam. It will be found during thesecond grinding that the 



balsam will resist the progress to some extent, but this 

 may be overcome by chipping it away as near to the 

 shells as can be done with safety. If sections show- 

 ing only internal arrangement are required, as in fig. 9, 

 after the half of the shell has been removed, the speci- 

 mens, to be cleaned from the balsam, may be left for 

 some time in absolute alcohol, taken out, and dried. 



In conclusion, it may be remarked that though the 

 study of this group of animal remains is hampered by 

 synonyms, yet the knowledge regarding them is distinctly 

 approaching something like order, and less like the 

 primitive undigested heap of biology alluded to by one 

 writer on the subject. Moreover, the knowledge can 

 only be extended by careful and accurate observations, 

 and any who are interested in the study of these minute 

 forms of life can add something to the general fund. 



<-;>t^^^5«^-• 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents^ nor can he take notice of anonymous com- 

 munications. All letters must be accompanied by the name and 

 address of the writer^ not necessirily for publication^ but as a 

 guarantee of good faith. 



TUBERCULOSIS FROM THE USE OF MILK. 



In the Chonikei- Zeititng for April 8th (p. 477) we read ; — 

 " The death of a child aged four months from tuberculosis 

 was traced by Prof. Demme, of Bern, to the use of the un- 

 boiled milk of diseased cows." The danger of the use of such 

 milk, though often denied, thus receives fresh confirmation. 



Zero. 



RESTS FOR AMPHIBIA IN AQUARIA. 

 I have often observed that the feet of newts, frogs, and 

 other amphibia kept in aquariums are rendered sore by 

 endeavouring to scramble up the rough stones often placed 

 to serve them as resting-places. I have found it better to 

 put in the aquarium stout pieces of flat cork, of a suitable 

 size, which may be kept in a suitable position by moorings 

 of iron wire, fixed to rock-work beneath the surface. 



Rana. 



THE NEW "SHELL-COLLECTORS' HANDBOOK." 

 Since the author of the " Shell-collectors' Handbook for 

 the Field " (Roper and Drowley) has replied to the criticisms 

 contained in your review of his book, and since a great 

 number of your readers are doubtless interested in shell- 

 collecting, I think a few additional remarks on the subject 

 may, perhaps, be acceptable. In your review it was, I 

 think, made clear that the present Handbook is calculated 

 to be of great use, and it certainly contains a fuller collec- 

 tion of varietal names and descriptions than any other book 

 which has yet been written for the use of British concho- 

 logists, and, as no desire was shown to find fault, only a very 

 few examples from the numerous errors and omissions 

 which a perusal had discovered were mentioned. Many 

 more of these, however, have since been pointed out in a 

 careful review in the Naturalist, from the pen of the Concho- 

 logical Society's recorder, and it is now only necessary to 

 reply to the points mentioned in the author's letter. In 

 reply to a remark, which was to the effect that the book con- 

 tained no notes on habits and distribution, and that such need 

 hardly have been omitted for the purpose of keeping the 

 volume within pocket-size, it is stated that " conchology is 

 essentially a field, and not a home, study"; but most people, 

 it is believed, while they collect in the field, retire to their 

 homes to study their finds. There are numerous omissions 

 which the statement in the latter part of the preface, that the 

 varieties described are " those which have been verified by 

 the Council of the Conchological Society or by the author," 



