168 APPENDIX TO REPORT ON OYSTER CULTURE 



problem of the specific influence of the soil is, however, a very difficult 

 and complicated one. First, because it is almost impossible to separate 

 the specific action of the soil from those of the other causes enumerated ; 

 and next, because, though much has been written on the subject of 

 oysters, I do not know of any systematic series of experiments carried 

 out upon different soils and for a sufficient length of time to enable 

 accidental causes to be eliminated, which could afford a clue to the 

 determination of the relative importance of the action of the several 

 causes above enumerated, at the different stages of development of the 

 oyster. 



In the absence of such experiments it is clearly worth while to give 

 the results of a comparative analysis of muds from well-known oyster 

 localities, made with a view of determining whether the chemical com- 

 position, or rather, the mineralogical character of the soil exercised any, 

 and if any, what influence upon the growth of oysters. For this pur- 

 pose the Royal Commissioners placed at my disposal a considerable num- 

 ber of specimens of soils from natural oyster beds, and from places where 

 artificial oyster cultivation had been tried either successfully or unsuccess- 

 fully. 



The remains of plants and animals mixed up with the sand or mud 

 in the small samples sent to me for examination could not, save in ex- 

 ceptional cases, be in such a state of preservation as to enable me to 

 determine with certainty the species to which they belonged. But even 

 were it otherwise, the small number of individuals, and the necessarily 

 very limited examples of different genera and species which such small 

 samples could contain, would give but a very inadequate idea of the 

 flora and fauna of each oyster bed, and of the adjoining littoral sea 

 bottom. ^n describing the character of each sand or mud I have, never- 

 theless, noted the plants and animals present (with the exception of the 

 microscopical ones), wherever the remains were sufficiently preserved to 

 enable me to do so. Generally the species observed were those which 

 seem to exist abundantly in most oyster grounds. 



I believe the character and abundance of Diatomacea and Rhizopoda, 

 and other microscopic animals, in oyster grounds, is of primary importance 

 in connexion with oyster cultivation. The green colour of the Colchester 

 and Marennes oyster shows how much the quality may be affected by 

 such organisms. It is probable that the action or influence of the soil of 

 oyster grounds upon the oyster at the various stages of its growth 

 depends mainly upon the nature and comparative abundance of the 

 Diatomacea, Rhizopoda, Infusoria, and other microscopical organisms 

 which inhabit the ground. I have accordingly always noted where the 

 mud appeared to be rich in Diatomacea, Foraminifera, and other micro- 

 scopic organisms. A thorough study of a few differently situated oyster 

 grounds exhibiting well-marked differences in the character of the oyster 

 from this point of view by a competent microscopist acquainted with the 

 classes of plants and animals just mentioned would be of great scientific 

 interest and practical importance. 



As the green colour of the mantle of oysters from certain localities 

 just referred to is commonly attributed to copper, and as such oysters 

 are consequently believed very generally to be poisonous, and their 

 value therefore greatly depreciated, I made the most careful search for 

 traces of that metal in the muds which I had received from grounds 

 known to produce green-bearded oysters. Oysters and other mollusca 

 placed in solutions containing copper and other metals absorb them, and 

 retain them in their tissues. I have had two or three opportunities of 

 examining oysters which had assimilated copper owing to mine-water 

 containing it being allowed to flow into estuaries at places close to oyster 



