56 THE MICROSCOPICAL NEWS. 
as Farrant’s solution, glycerine, or jelly, were sometimes preferable 
where tissues were of a very hyaline nature, but with objects requir- 
ing a maximum amount of light for their illumination, especially 
for use with the polariscope, balsam was, from its highly refractive 
nature, very suitable. Mr. Miles afterwards mounted successfully 
several specimens of the head of the honey bee in pure balsam 
without pressure, a method of mounting advocated by many, but 
not generally adopted, in consequence of manipulative difficulties. 
Increased interest has recently been excited by some beautiful 
entomological preparations thus mounted and sold by Mr. Frederick 
Enock, of London. ‘These mounts command a comparatively 
high price; hence the ability to prepare objects in this manner 
is worth acquiring by the student in microscopy. Apart from their 
value as show objects, these mounts are almost indispensable 
as aids to a correct knowledge of the disposition of parts—the 
relation which one organ bears to another—a knowledge of which 
should always precede the investigation of a particular organ with 
high powers. Two difficulties are usually met with in the putting 
up of this kind of mount—imprisonment of air bubles and shrink- 
ingage of the medium by evaporation—to obviate which, in the use 
of balsam, a new cell, having alternate elevations and depressions, 
has been devised by a member of the section, in the use of which, 
by leaving an excess of balsam round the cell and cover glass, air 
bubbles ultimately escape through the spaces, and loss by evapora- 
tion of essential oil in the balsam is provided for. Mr. Miles 
incidentally remarked that the preparations of Mr. Enock were, he 
believed, put up in glycerine, a medium he would make use 
of some evening when fluid mounts were under consideration. 
Mr. E. Ward illustrated mounting in balsam and benzole. The 
addition of benzole to balsam renders it more fluid and less difficult 
to work with, but in selecting Polycystina and Spicules to work 
upon Mr. Ward had to face difficulties which, under his skilful 
manipulation, were not apparent. Few microscopists have the 
opportunity of seeing Polycystina alive, and besporting themselves 
in their native element, the sea, but nearly all are familiar with the 
beautiful siliceous skeletons of these minute creatures. They are 
found plentifully in a fossil state in Bermuda, Sicily, Virginia, and 
Barbadoes. ‘They are of wonderful beauty and variety of form ; 
are more or less perforated and covered with spines and projections, 
through which the sarcode body when alive extends itself into 
pseudopodial prolongations. When seen besporting themselves in 
all their living splendour, their brilliancy of colouring renders them 
objects of unusual attraction. ‘They are met with on the surface 
of the Atlantic, Pacific, and other Oceans, and were obtained in 
Mid-Pacific at 2,425 fathoms during operations by the Challenger 
ten years ago. 
