192 
PENNATULIDA. 
distinguishing clearly the transparent tissues in the sections. 
In the case of the Funiculina and Pennatula polypes, which 
both contain a number of hard calcareous spicules, these 
have also to be decalcified before the sections can be cut, by 
soaking the object in very dilute hydrochloric or nitric acid 
for a week or fortnight; a very gradual process being desirable 
in order to avoid any evolution of gas in the tissue that might 
cause some rupture or displacement. 
The object is then imbedded in paraffin in a small paper 
trough or mould, not larger than enough to insure a margin 
of paraffin of not less than J ,h inch on all sides beyond the 
object. Some melted paraffin is poured into the mould, the 
object is laid centrally upon this, and the mould filled up 
with melted paraffin; the whole is then exposed to a uniform 
temperature of 130° or 140° Fahr. in a soaking chamber of a 
water-oven for a whole day, for the purpose of getting the 
paraffin thoroughly to permeate the tissues of the object. 
This is a point of special importance, as it is requisite to have 
the whole like a thoroughly solid block of paraffin in order to 
obtain sound unbroken sections. Also it is necessary to 
employ paraffin of the exact degree of hardness and stiffness 
according to the temperature of the room in which the section¬ 
cutting is to be done, that will give sections tough enough 
not to break, and soft enough to stick together at their edges, 
without being so soft as to stick to the razor, which is used 
quite dry and clean. This point is obtained by selecting the 
paraffin from several different qualities, which can be obtained 
having melting points at different temperatures, and varying 
the selection according to the seasons of the year and 
circumstances of the room. This plan is found, with a little 
practice, to yield the most satisfactory results, the material 
being homogeneous, and working better in the cutting than 
any mixture of oil or other material with the paraffin to 
modify its hardness. 
A holder is then made for the object whilst being cut, by 
a small brass tube as a mould, closed at the bottom with a 
cork, and filled with melted paraffin, into which, when set, 
the little paraffin block containing the object is fixed by 
making a central cavity with a hot wire, and bedding it in 
solid by melting the paraffin around it with the hot wire, 
leaving the little block projecting partly at the top. The 
projection is pared away carefully until the imbedded object 
is seen to be near the surface, and the sides are pared away 
into a square form with parallel sides, leaving only such a 
margin at the sides beyond the object as is found by experience 
to supply sufficient strength to the sections to hold together 
when cut, without incumbering them with any superfluous 
