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__‘IL—ADDITIONS TO THE FAUNA OF THE FIRTH OF 
a : FORTH. (Pls. IL-V.) 
* 
. Parw.¥.,. By;Tsomas Scort, F.L.S. 
In this—the fifth—contribution towards a better knowledge of the 
invertebrate fauna of the Firth of Forth, only the lesser crustacea, and 
chiefly the copepoda, are dealt with. There are several points of interest 
in the natural history of the Forth crustacea referred to in this contribu- 
tion: it is shown, for example, that the genus Longipedia, which has 
hitherto been considered to comprise only one species—Longipedia 
_ coronata—included not only a distinct variety (if it be not a distinct 
species) of the same genus, but also a supposed sexual form, for which it 
has been found necessary to provisionally institute a new generic name. 
- Some of the species, though only now recorded for the first time for the 
_ Firth of Forth, were collected so long ago as 1889, but were allowed to 
stand over for want of sufficient information concerning them. 
In preparing this paper, I have again the pleasure of thanking the kind 
friends mentioned in my papers of previous years for assistance and 
- encouragement. I have also gratefully to acknowledge the kindness and 
sympathy of the following eminent French naturalists who have corre- 
sponded with me on matters relating to the subject of these papers :— 
MM. Le Baron Jules de Guerne and Jules Richard, Dr Raphael Blanchard, 
Dr Eugene Canu, and Dr Georges Roche. The drawings which accompany 
this paper are the work of my son, Mr Andrew Scott, who has also pre- 
pared the greater part of the necessary dissections. To carefully dissect 
a copepod, some of which are not more than the thirtieth to the fiftieth 
of an inch in length, requires no little detexerity ; yet a complete series of 
dissections are often prepared from a single specimen. It is only by such 
careful work that I have been enabled to add so many rare and interest- 
ing species to the number of the Forth crustacea. 
Perhaps the following brief statement of the method pursued by 
my son may be of interest to other students:—When necessary, the 
specimen is left to soak for a time in caustic potash, but this, while it 
clears the tissues, has sometimes a tendency to cause the specimen to 
shrivel up more or less, and not only while it remains in the caustic 
potash, but also after it is mounted in glycerine jelly—which is the 
medium generally made use of for mounting. To overcome this difficulty, 
the specimen, after being removed from the caustic potash, is well washed 
in fresh-water, which restores it to its normal form. If a full-sized draw- 
ing is wanted, and the specimen still shows a tendency to shrink in the 
glycerine jelly, it is simply mounted in water under a cover-glass till the 
full-sized drawing is made,—three or perhaps four tiny bits of stout paper 
being inserted at intervals under the edge of the cover-glass to keep it: 
from pressing or the specimen’ The manner in whick shrinkage usually 
takes place is by the contraction of the tissue between each body segment, 
so that the one segment is more or less drawn in under the other-—tele- 
scope fashion—and the specimen becomes in this way apparently shorter 
and more robust than it should be; it is seldom that mounting in 
_ glycerine jelly makes any difference on the dissected appendages of the 
__ copepoda. When the specimen is to be dissected, it is placed in a little 
water on a slide on the stage of the microscope—a one-inch objective is 
the power used—with a fine needle, the thick end of which has been 
pushed into a small bit of common timber for a handle, and fixed with 
a 
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