ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 601 



3. The naphtha solves the solid paraffin quicker than turpentine 

 does. 



4. No traces of indiarubber are visible after mounting, since india- 

 rubber becomes perfectly transparent in balsam. 



These methods have been put to a rigorous test by Mr. Caldwell 

 and are now in use in the Morphological Laboratory of Cambridge 

 University. 



Sealing up Preparations.* — Dr. C. Norner, of the Veterinary 

 Institute of Vienna, describes a method adopted there by Prof, 

 Csokor for the above purpose. ^ 



Take the ordinary commercial resinous turpentine, break it into 

 small pieces, and dissolve them in a water-bath, then pour the liquid 

 into another vessel and let it cool. A hard, dark-brown, brittle mass 

 is thus formed upon which the pressure of the finger makes no 

 impression. A little of the resinated oil of turpentine may be added 

 to the liquid, but the whole must be heated for several hours in the 

 water-bath in order to obtain the requisite degree of hardness on 

 cooling. 



The turpentine thus prepared is placed on the cover-glass by 

 means of a heated knitting-needle (fixed on a piece of wood), the 

 other end being bent at right angles for about 15-18 mm. to corre- 

 spond with the width of the cover-glass. The bent end being pressed 

 into the turpentine and withdrawn, the turpentine adhering to it is 

 spread out on the margin of the cover-glass, and this repeated until it 

 is completely surrounded with turpentine, which is finally drawn a 

 little over the edge. Care, however, must be taken not to overheat 

 the needle so that the glass cracks. If the cover-glass should not be 

 sufficiently firm, or if any glycerine still remains on the edge, a com- 

 bination of gold size and turpentine may be used. The gold size has 

 the advantage of agreeing well with the glycerine, so that it is not 

 necessary to remove the latter completely. When the gold size is 

 dry a second layer of turpentine may be put on. The author generally 

 uses this combination to inclose worms, when the cover-glass cannot 

 be completely closed on all sides in consequence of the thickness of 

 the object. The ring of turpentine may be laid over the gold size 

 without detriment. 



The method of sealing glycerine preparations by turpentine has, 

 the author says, the great advantage of extraordinary durability. The 

 object so prepared can also be cleaned at any time with a piece of 

 wash-leather without the fear of injuring it by too much pressure. 

 An additional layer of varnish, which is absolutely necessary for 

 gold-size and other preparations, is dispensed with by this method of 

 treating glycerine preparations with turpentine. It has the dis- 

 advantage of being more tedious than in the case of gold size, but 

 practice soon brings dexterity. 



Opaque Dry Mounts. f — Mr. J. E. Fawcett prepares opaque dry 

 mounts by building up on the turntable a cell with hot wax partly on 



* Arch. f. Mikr. Anat., xsi. (1882) pp. 351-4. 

 t Micr. News., iii. (1883) pp. 153-4. 



