ON MOUNTING. 137 



parations mounted by him in Farrant's medium, and 

 has listened sympathetically to the sorrows and 

 disappointments of those who find " the difficulties 

 of mounting in Farrant's medium insuperable ; " he 

 has also read of a clumsy and absurd arrangement 

 for passing this medium through a funnel stuffed 

 with cotton wool, which is supposed to eliminate 

 the air whilst ensuring the agreeable addition of 

 cotton fibres to the slide in place of air bubbles. 

 He can only say that he has had great practice with 

 and experience in the use of Farrant's medium 

 during many years, and has found no difficulty 

 whatever in getting rid of air bubbles. Here again 

 he advises put an abundant supply, with a glass 

 rod, on to the slip, place the specimen, which should 

 be immersed in Farrant's medium for twenty-four 

 hours before mounting it, in the centre of the drop. 

 If there are any large air bubbles, as there possibly 

 may be, explode them with a red hot needle or push 

 them to the margin of the drop, where they will 

 disappear at once. If there are any large air 

 bubbles in the specimen, remove these also with a 

 needle ; small bubbles will disappear by absorption 

 within a day or two. Finally, do not press down 

 the cover too much afc first so as to cause too great 

 an exudation, from under it, of the medium ; leave 

 it resting lightly upon the specimen for a few days 

 during which all bubbles, if any, will go, and the 

 medium will " set " to some extent ; then press 

 down the cover, and the medium having so " set " 

 will not again be drawn under the cover by capillary 

 attraction to anything like the extent that it is 

 when first applied ; and this pressing down of the 

 cover can be repeated several times at intervals of 



