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III.— MATERIAL AND METHODS. 
We have used three distinct species of oyster, and many local varieties, or races, 
from various parts of the European and American coasts. The species are the 
following : — 
1. Ostrea edtilis, Linn., the common edible oyster of North-west Europe, the species 
to which our " Natives," " Deep-sea oysters," " Rock oysters," " Pandores," and 
many other kinds from our own and neighbouring coasts belong. We have 
had samples of these from Colchester, Pyefleet, Mersea, Roach River, Leigh, 
Plymouth, Falmouth, Jersey, Wales, Isle of Man, Lancashire, the Scheldt, 
Nieuport, Spezia, and the West Coast of France. 
2. Ostrea virginica, Gm., the American oyster : very commonly " laid," " bedded," 
or stored on various parts of our coast. We have had samples of " East Rivers," 
" Sounds," and " Blue Points," direct from America to Liverpool ; and of those 
that have been bedded in this country for longer or shorter periods, from Dublin, 
Carlingford, Fleetwood, Brightlingsea, Leigh, Falmouth, and the Menai Straits. 
3. Ostrea ( Gryphcea ) angulata, Lamk., the Portuguese oyster of Southern and 
Western Europe. We have had samples of this from Arcachon in the South- 
west of France, and from Falmouth, Leigh, and the estuary of the Colne.* 
All the oysters have been examined in the first place alive, and their characters 
noted: coloured sketches have been made of many. In some cases the gills and other 
parts have been examined fresh, in teased and pressure preparations ; but in all cases 
pieces have also been fixed, preserved, and sectioned. We have employed a variety of 
methods. Some gills and pieces of liver and intestine have been frozen in gum and cut 
at once with the freezing microtome, in order to have sections of the fresh tissue unstained 
for comparison with the sections which have undergone treatment with re-agents. 
We have obtained the best results from our sections of mantle lobes, gills and 
viscera which had been fixed in corrosive sublimate and acetic acid, washed with 
alcohol, and then put through increasing strengths of alcohol, and finally iodine dissolved 
in 90 per cent, alcohol, cleared in either turpentine or xylol, imbedded in paraffine, cut 
with the Cambridge Rocking microtome, stained in eosine and haematoxylon, and 
mounted in balsam. Some of our preparations were fixed in 5 per cent, solution of 
formol in place of corrosive and acetic. The washing with iodine and alcohol was 
sometimes deferred until the sections were on the slide, previous to staining. 
The Histo-Chemical and Bacteriological methods will be stated below in Sections 
IX. and XIV. respectively. 
* We are much indebted to several gentlemen for kindly taking trouble to supply us with the special kinds 
of Oysters we desired. We would especially thank Charles Petrie, Esq., C.C., and Geo. T. G. Musson, Esq., of 
Liverpool ; Rupert Vallentin, Esq., of Falmouth ; Dr. P. P. C. Hoek, of Helder ; Dr. J. G. de Man, of lerseke, 
and Dr. J. M. Bottemanne, of Bergen-op-Zoom, in Holland ; and also Dr. Murie, and Mr. James Homell of Jersey. 
