10 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Hardening of Balsam. — In works on the 

 microscope where any directions at all are given for 

 hardening objects mounted in balsam, they are so 

 elaborate and troublesome that I think the following 

 simple remarks on the subject may be of some 

 practical use. The process I have used for some 

 time with complete success is as follows : — The 

 object and a moderate quantity of balsam are 

 covered with thin glass in the usual way, and if the 

 object is small, held down with a spring clip to 

 prevent displacement. The slide is then boiled 

 either over a spirit-lamp or, better still, over an 

 ordinary microscopic lamp. Vapour of turpentine 

 is freely given off, which, as the slide cools, contracts, 

 drawing under the superfluous balsam, which should 

 be kept round the glass cover with a needle. When 

 cool, the balsam may be chipped off with a knife, 

 and the slide finished in the usual way. The cover 

 can never be displaced, as is too often the case 

 where the slide is not boiled. A little practice will 

 tell when the boiling has gone far enough, as, if con- 

 tinued too long, ihe bubbles formed during the 

 process will not disappear, and the slide will be 

 spoiled. — C. C. Underwood, Royal Institution, Albe- 

 marle Street. 



Reproduction of Desmids. — The American 

 Nahiralist states that Prof. Leidy, at a late meeting 

 of the Academy of Natural Sciences of Philadelphia, 

 made some remarks on the mode of reproduction 

 and growth of the Desmids. In illustration he 

 described a common species of Docidium or Ple/iro- 

 tcenium. This consists of a long cylindroid cell, 

 constricted at the middle, and slightly expanded 

 each side of the constriction. When the plant is 

 about to duplicate itself, the cell wall divides trans- 

 versely at the constriction. From the open end of 

 each half-cell there protrudes a colourless mass of 

 protoplasm defined by the primordial utricle. The 

 protrusions of the half-cells adhere together, and 

 continue to grow. The bands of endochrome now 

 extend into the protrusions, and subsequently keep 

 pace with their growth. The protrusions continue 

 to grow, until they acquire the length and form of 

 the half-cells from which they started. The exterior 

 of the new half-cells thus produced hardens or 

 becomes a cell wall, like that of the parent half-cells. 

 In this condition two individuals of Docidium are 

 frequently observed before separation. During 

 the growth of the new half-cells the circulation of 

 granules in the colourless protoplasm is quite active. 

 In a species of Docidium lh m.m. long by T V m.m. 

 broad, the growth of the new half-cells was observed 

 to be at the rate of about i m.m. in an hour. 



SpHyERAPHIDES IN UltTICACEiE AND LeONURUS. 



—In the last number of the Jlonthhj Microscopical 

 Journal, Professor Gulliver, after referring to the 



continental observations, and to those of Mr. Roper 

 in a late number of Science-Gossip, on the crystals 

 in the leaf-blade of the Wall-pellitory, describes two 

 kinds of spbeeraphides in all the British TJrticacese. 

 The largest and smoothest, pervading the leaf" 

 blade, are composed of carbonate of lime, and the 

 smallest and roughest, forming chains in the pith 

 and leaf-nerves, consist of oxalate of lime. Though 

 neither raphides nor other crystals have been 

 heretofore noticed in British Labiatese, the spha> 

 raphides thickly dotted in the leaf-blade of Leonuriis 

 Cardiaca, or the Motherwort, are large and remark- 

 able, and are composed of carbonate of lime, while 

 the smaller sphaeraphides in the leaf-nerves of this 

 plant consist of oxalate of lime; but the pith of 

 Leonurus is destitute of sphfjeraphides. Thus these 

 plants afford good examples of two kinds of spbee- 

 raphides, differing both in form and chemical 

 composition, occurring together in one and the 

 same species ; and these crystals are described as 

 beautiful microscopic objects, easily displayed, and 

 admirably suited for preservation, either dry or in 

 glycerine, on slides for the enrichment of the micro- 

 scopic cabinet. 



An Evening at the Royal Microscopical 

 Society.— At the " scientific " meeting of the Royal 

 Microscopical Society, held at King's College on the 

 evening of the 9th December, an unusually inter- 

 esting series of exhibits was shown, illustrating 

 the progress of optical und mechancial ingenuity in 

 the development of the instrument, which is rapidly 

 becoming an indispensable article of furniture in 

 homes where intellectual culture is promoted, all 

 over the world. One could not help being struck, 

 after a cursory survey of the instruments, at the 

 variety; in the patterns. First, Powell & Leland 

 exhibited two of their superb microscopes. In one 

 of them the lines of Amphipleura pellucida were 

 being resolved with a ?-inch objective, a feat never 

 before attempted. In the other, an §th was being 

 made to show the dots on P. angulatum, under the 

 very worst conditions, namely, full aperture of the 

 achromatic condenser, conditions under which none 

 but the most perfectly constructed objectives would 

 show anything but flare and indistinctness. Then 

 there were several splendid examples of Stephen- 

 son's binocular. One of them, that belonging to 

 Mr. Stephenson himself, was displaying some 

 exquisitely beautiful crystals of sulphur, deposited 

 (so we understand) from bisulphide of carbon upon 

 a glass slip. Several of the new pattern Ross in- 

 struments, designed by Mr. Wenham, were being 

 employed to show various objects. One of them 

 was exhibiting a piece of rock crystal (we think) 

 containing minute cavities, in each of which a 

 molecule was in perpetual motion — a perfectly in- 

 explicable puzzle. In another part of the room 

 a tolerably good result was being obtained with 



