ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 317 



frozen they should be quickly transferred to the glass slide on which 

 they are to be mounted. On touching the glass, the slice of jelly 

 almost immediately thaws and adheres as a consistent fibre to the 

 surface. When enough slices have been placed on the slide, they 

 should each be covered with a drop of glycerine (the sooner this is 

 added the better) ; a cover-glass is then superposed, zinc white or 

 some similar cement is run round it, and the preparation is complete. 

 In process of time the glycerine will permeate the gelatine and 

 convert it into glycerine jelly ; if this does not take place soon enough, 

 it may be hastened by placing it in an oven kept at a temperature of 

 about 20° to 30° C. 



In this way a series of entire slices of great thinness may be 

 obtained from the most disconnected structures ; even when they con- 

 tain hard silicious spicules, as in the case of sponges. 



Diatoms may be cut without difficulty by this method, and the 

 author says he has now beside him some slices of Pleurosigma which 

 reveal the internal anatomy of these in an admirable fashion. It 

 need not be added that the process effects a considerable saving in 

 labour and time. 



Mayer's method of Fixing Sections.* — P. Mayer proposes an 

 improvement on the methods of Frenzel, Threlfall, and Schallibaum. 



A mixture of equal volumes of filtered white of egg and glycerine 

 is made, and spread with a fine brush in a very thin and uniform layer 

 on a cold slide. The sections are then laid on it, and the whole warmed 

 for some minutes on a water-bath ; they can now be treated with oil 

 of turpentine, alcohol, water, and colouring reagents, without any 

 danger of their moving. The glycerine only serves as a means of 

 keeping the surface of attachment moist ; if the paraflSn in the sections 

 melts, it immediately carries away the albumen, so that the neigh- 

 bourhood of the section is almost or altogether freed from it, and this 

 is an additional advantage of the method. The mixture of albumen 

 can be kept clear by the use of antiseptics (carbolic acid). 



Alum-carmine and strong alcoholized solution of carmine are very 

 useful staining reagents. The latter is slightly modified from the 

 well-known preparation of Grenacher in that 4 gr. of carmine are 

 dissolved in 100 ccm. of 80 per cent, alcohol, with the addition of 30 

 drops of concentrated pure hydrochloric acid, heated for about half 

 an hour in the water-bath ; this solution is filtered, while still hot, and 

 the superfluous acid is carefully removed by the addition of caustic 

 ammonia, added till the carmine begins to be deposited. When quite 

 cold this solution stains very rapidly (for example, embryos of lobsters 

 are stained in about a minute) and intensely, though diffusely; 

 washing in alcohol acidulated with hydrochloric acid is therefore 

 necessary if the nuclei alone are to be stained. The moment of 

 satisfactory cleansing may be judged by the appearance presented by 

 the albumen, which will completely give up the carmine to the alcohol, 

 or will, at most, be only faintly coloured. 



* MT. Zool. Stat. Neapel, iv. (1883) pp. 521-2. 



