ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 635 



Born makes use of three rectangular tin boxes of equal eizcR, each 

 measuring 270 mm. x 230 mm. x ^^ mm. Sections should be made 

 about 1/25 mm. thick (never thinner than 1/50 mm.). If we desiro 

 to construct a model of an object from serial sections 1/30 mm. thick, 

 which shall be magnified 60 diameters, then the wax plates must be 

 made 60 times as thick as the sections, i. e. 2 mm. thick. 



The surface of a plate that could be made in a box of the above- 

 named dimensions, contains 62,100 sq. mm. ; and the volume of such 

 a plate 2 mm. thick would therefore be 124*2 c.cm. The specific 

 gravity of common raw beeswax amounts to •96--97. For use, it 

 requires only to be melted and a little turpentine added to make it 

 more flexible. Thus prepared, its specific gravity is about "95 ; and 

 this number has been found sufiiciontly accurate in all cases. The 

 weight of the wax required to make one plate of the above size, will 

 accordingly be 117 '99 gr., or, in round numbers, 118 gr. The wax 

 having been weighed and melted, the tin box is first filled ^ cm. 

 deep with boiling water, and then the melted wax poured upon the 

 water. If the water and the wax are quite hot, the wax will gene- 

 rally spread evenly over the surface ; if gaps remain, they can be 

 filled out by the aid of a glass slide drawn over the wax. As soon as 

 the plate has stiffened, and while it is still soft, it is well to cut it 

 free from the walls of the tin box, as further cooling of the water and 

 the box might cause it to split. By the time the water becomes 

 tepid, the plate can be removed from the water to some flat support, 

 and left till completely stiffened. Half a hundred plates may thus be 

 prepared in the course of a few hours. 



The outlines of the section are transferred to the plate in the 

 following manner : a piece of blue paper is placed on the plate with 

 the blue side turned towards the wax, and above this is placed a sheet 

 of ordinary drawing paper. The outlines are drawn on the latter by 

 the aid of a camera, and at the same time blue outlines are traced on 

 the wax plate. The plate can then bo laid on soft wood and cut out 

 by the aid of a small knife. Thus a drawing and a model of each 

 section are prepared. The plates thus prepared can bo put together 

 in the proper order, and fastened by the aid of a hot spatula applied 

 to the edges. 



Shrinking Back of Legs of Oribatidae in Mounting.* — A. D. 



Michael suggests a mode of getting over the difficulty of the shrinking 

 >>ack, during the process of mounting, of the legs of species of Oribata 

 and other genera which have special cavities for the reception of the 

 legs. The process requires careful manipulation, but if well done is 

 very successful. Place a very thin layer of balsam upon the slide 

 upon which the specimen is to be soaked in oil of cloves ; when this 

 layer Vjccomes sticky the specimen is placed upon it, dorsal surface 

 downwards. The mounter must then extend the legs and stick thorn 

 to the balsam, if thoy rise up they should be pressed down again with 

 a hair ; when they are all fast the body should be brushed over with 

 the smallest possible quantity of oil of cloves to prevent its drying, 



* ' Britieh Oribntidse ' (Ray Society) 1884, pp. 104-5. 



2 i; 2 



