8 THE NORTHERN MICROSCOPIST. 
they enhance considerably the pleasures and study of a country 
walk by giving us a fixed object in our walk ; they are splendid as 
a study on account of their beauty of colour and variety of form ; 
they are parasitic on living, dying, and dead leaves, and therefore 
obtainable all through the year. 
THE EXAMINATION AND PRESERVATION OF 
INFUSORIA. 
ITH the lower powers of the microscope scarcely any instruc- 
tions are needed for the observation of Infusoria, but as many 
of them require the use of high powers, a few remarks showing how 
to proceed in such cases may not be out of place, but rather of 
assistance to the student. 
Infusoria are generally attached, sometimes to leaves and stems 
of aquatic herbs, at others to the fronds of algze, while not a few 
are to be met with encrusting floating bodies such as pieces of stick 
and straw, or even upon the shells or carapaces of the Crustacea. 
Some of these large opaque bodies, or rather the organisms upon 
them, are exceedingly difficult to view with high powers, such as 
the one-eighth, but if the object be laid upon a slide and a thin 
glass cover placed on the spot to be examined, a little water being 
‘added under the cover with a curved pipette, capillary attraction 
will often retain sufficient to enable the observer to examine the 
object without much difficulty. The value of immersion objectives 
is here set forth, as in this case it is only necessary to immerse the 
object in a shallow stage trough, and focus into the water upon 
the object sought. 
The organisms upon stems of water plants, or on other cylindrical 
bodies, are examined without so much difficulty: a piece snipped 
off with the scissors may be laid upon a slide and covered with 
thin glass, and by having a film of water between the two, the 
examination is easily performed, even with high powers. It may 
happen that the stem or other host is too thick, and therefore 
sections will have to be made of it; but this is a very easy opera- 
tion with an ordinary scalpel, and the assistance of a watchmaker’s 
or engraver’s eye-glass. 
Leaves are more difficult of examination, the best objects are 
sure to be situated in a plane at right angles to that of the leaf, so 
that a live box is of but little use “unless the characteristic part of 
the organism is near the edge. 
