236 



HARDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, 1869. 



MICROSCOPY. 



A New Cell. — No one can better understand the 

 difficulties which a young microscopist meets with, 

 than he who has been compelled to fall back upon 

 the resources of his own inventive capacities to meet 

 those emergencies which present themselves on the 

 very threshold of a new study. Perhaps one of the 

 first of these difficulties is the formation of a cell. 

 Our standard works on the microscope seem to give 

 us an exhaustive stock of information on this point, 

 but yet this question remains unanswered, viz., — 

 How to prepare at the lowest cost a large stock of 

 neat and efficient cells ? The merest tyro is aware 

 that a revolving disc, a diamond pencil, &c., will 

 supply means for the construction of neat cells ; but 

 all this involves a certain outlay which many would 

 hesitate to expend. A steady hand can draw a fair 

 circle of Brunswick black on a slide, but in order 

 that the cell should be deep, each successive layer 

 should be firmly dried before the application of a 

 second, and the various annoyances which this plan 

 often gives rise to are known only too well to those 

 who are practically familiar with this method. But 

 purchase a box of endless elastic bands,* and the 

 addition of a jar of Brunswick black will now supply 

 all the requisite material for the formation of a large 

 stock of good and neat cells. Slip one of these bands 

 on to the blades of a pair of scissors, slightly opening 

 the latter to keep the band near the points, and 

 prevent it from slipping off; now paint it over with 

 a thin layer of Brunswick black, allow the band to 

 fall fiat on the centre of a glass slide, fix your object, 

 and gently place your thin cover over it, which will 

 firmly adhere to the band; this is cell No. 1. Eor 

 cell No. 2 another band is slid on to the scissors after 

 the first band has been painted ; the pressure of a 

 forceps will cause them to adhere, and now you have 

 your cell double the depth of the first. The bands 

 which I use are \ an inch in diameter, and with 

 these the deepest cell advisable to be made is that 

 of three bands ; should a deeper cell be required 

 bands of a larger diameter are necessary. I have a 

 large number of objects mounted in this way, the 

 majority being dry preparations, but I find this cell 

 is equally serviceable for mounting in glycerine or 

 Goadby's solution. The diamond pencil, revolving 

 disc, moulded cell, &c, are all desirable acquisitions, 

 but for my own part I prefer the elastic cell on ac- 

 count of its neatness and simplicity. Should any of 

 your readers feel inclined to try this method I can 

 confidently assure them they will find it the cheapest 

 and most satisfactory. — W. Bevan Leicis, L.R.C.P. 

 Lond. 



Markings of Diatoms. — Having just been 

 reading Mr. Reade's curious investigations upon 



* Sold by W. Warne & Co., also by Perry & Co 



diatoms with the equilateral prism (see Journal of 

 the Royal Microscopical Society for July and 

 August), I took up a slide of Triceratium favus, and 

 viewing it with an eighth object glass, by parallel 

 rays, I noticed that the areola; possessed the same 

 property as the corueules of the compound eyes of 

 insects, so that the image of any object, interposed 

 between the mirror and the stage, was seen in each 

 of them. Looking afterwards at a beetle's eye under 

 the same power and illumination, I was surprised to 

 notice how exactly the same effects might be pro- 

 duced upon it as upon the triceratium, by slightly 

 altering the focus of the object-glass or the position 

 of the mirror. Spherules, hexagons, or pyramids, 

 were equally produceable at will in either slide. 

 May not our knowledge of the one give some clue 

 to the real formation of the otber ? By careful 

 focussing, a double layer of structure may be seen 

 in the Triceratium valve, very similar to that of 

 Heliopelta ; each apparent hexagon being made up 

 of a series of circular areolations, three forming 

 each side of the hexagon, and seven in the centre ; 

 while on altering the focus the upper surface of tbe 

 valve gives the appearance of large nodules, as de- 

 scribed by Mr. Reade. — R. 



Hints for Workers. — Your interesting article 

 on the sertularians set me thinking of what a pity 

 it is that our rapidly increasing class of amateur 

 microscopists should not be urged to take every 

 opportunity of adding to their knowledge of natural 

 history in all branches, so as to insure the greatest 

 possible accuracy in the nomenclature of their 

 slides. Eor my own part I take the greatest pains 

 to secure this accuracy. I like to have my labels 

 as detailed as possible in their information, showing 

 where necessary, class, order, section, family, genus, 

 and species ; and I never regret having to change 

 these labels on any increase of knowledge. This is 

 one of the manners in which amateur microscopy 

 can be made really educating, and not a mere mania 

 for the collecting of pretty slides. Yet I know cabi- 

 nets where the organisms which your article has 

 described are simply labelled as "corallines," a 

 name which though at one time received has now 

 become entirely inappropriate, because unfortunately 

 it is now applied only to a division of plants (Algee) 

 while the sertularians are certainly animal. Being 

 on this subject I cannot avoid appealing to you and 

 to your readers (though it is somewhat presump- 

 tuous in me to differ thus from Mr. Hincks) as to 

 whether it is not a pity to revive the term " zoo- 

 phyte," as applied to this or to any division of 

 polypes. As implying more than we know, or I may 

 say what we know to be false ; they are not animal 

 plants (to translate the word), but simply and en- 

 tirely animal. And is it not unnecessary where 

 polyzoa, or bryozoa, would answer as well ?— 

 /. G. H. 



