ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 509 



Fig, 148 shows the instrument as arranged for the spray. The gum- 

 imbedded object placed on the zinc plate Z is frozen by means of a spray 

 of anhydrous ether contained in the vessel having the tubes T. The 

 superfluous ether runs down through the tube P to a collecting bottle. 

 The spray-tubes are fixed in a slot under Z, so that they are easily re- 

 moved if required. Instead of the hand-bellows N a pedal pump can be 

 employed. There is an indicator at E, The zinc plate Z is insulated 

 from the surrounding metalwork by means of a vulcanite casing. When 

 used with ice, the glass plate L, the supports M and M', and the spray 

 apparatus are removed ; Z is unscrewed, and replaced by the plug K, The 

 glass plate L is next fitted on the brass plate B, and then the instrument 

 is ready for use. When the box C is filled with the ice and salt mixture 

 the tube H is kept plugged until the box becomes quite full of water. 

 The gum solution is poured into the well and the object immersed therein. 

 The mouth of the well is then closed by means of a guttapercha sheet fixed 

 down by a flat leaden weight, and the whole instrument wrapped up in 

 flannel until the freezing is complete. 



A special advantage claimed for this instrument is the facility with 

 which delicate sections are removed from the knife into water, or at once 

 on to the slide. 



The knife required for this instrument is of a special construction, and 

 when used is pushed over the glass plate and across the well at a right 

 angle. Hence the knife does not remain sharp very long. 



Machine for cutting Rock-sections.* — The machine devised by Dr, H. 

 Eauff does not differ in principle from those which are ordinarily used, but 

 it is provided with adjustments of a new form, by which the rock-specimen 

 may be firmly fixed in any desired position with respect to the cutting-disc. 

 The construction is that of an ordinary turning-lathe, the disc being worked 

 by a treadle and grooved flywheel, while the specimen is held in a support 

 which slides along the horizontal slot of the lathe-bench, and is clamped by 

 a nut from below like the movable rest of a turning- lathe. The rock is 

 held, not by cement as is generally the case, but in a vice capable of holding 

 large fragments : the block which carries this vice is provided with two 

 horizontal rectilinear sliding movements at right angles to one another, one 

 of which is worked by a screw- worm and handle, and the other by a weight 

 acting over a pulley, which keeps the rock in continual contact with the 

 cutting-disc. In addition to these movements the vice-piece can also rotate 

 about a vertical and horizontal axis, and the plate to which it is attached is 

 adjusted and fixed by four levelling-screws. The bearings of the axle and 

 the various parts of the machine are made so massive as to insure greater 

 stability than such machines generally possess. 



Sections of CMtinous Organs.f — Herr P. F. Breithaupt, in his inves- 

 tigations into the structure of the bee's tongue, made use of eau de 

 Labaraque (subchloride of potassium), which, after long-continued treat- 

 ment, dissolves chitin, while it has a preservative action on the neighbouring 

 tissues. The concentrated solution of eau de Labaraque was diluted with 

 three to four parts of water. After washing with water and 35 per cent. 

 alcohol the preparations were hardened by absolute alcohol, cleared uj) in 

 oil of cloves and imbedded in Canada balsam ; those which were adapted 

 for cutting were, after treatment with oil of turpentine, imbedded in a 



* Verh. Naturhist. Ver. Preuss. Rheinlande, xliii. "(18S6) Corr. Bl., pp. 130-9 

 (3 figs.), 



t Arch, f, Naturgesch., liii. (1886) pp. 53-5. 



