of the Fishery Board for Scotland. 



197 



II. — ADDITIONS TO THE FAUNA OF THE FIRTH OF 

 FORTH. (Pis. II.-V.) 



Part V. By Thomas Scott, 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 P'orth 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 on the specimen. The manner in which 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" 



