( 6) 



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 : — 



i. Ostrca edulis, 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. Ostrca 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. Ostiea (Giyphcca) 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 Ierseke, 

 and Dr. J. M. Bottemanne, of Beigcn-op-Zoom, in Holland; and also Dr. Murie, and Mr. James llomell of Jersey. 



