ARTIFICIAL OYSTER CULTIVATION. Il6l 



which we have more fully entered into under the head of 

 " Inanimate Enemies." (<?) 



As regards chemical composition, the soil of a locality, 

 to be employed successfully as a fattening place, must 

 contain more or less flocculent silt, highly hydrated, and 

 rich in organic matter, i.e., in those microscopic organisms 

 which are known as Diatoms, Infusoria, Foraminifera, 

 Rhizopoda, &c., as the presence of these animalcules and 

 Algce are the true test of a good oyster ground. The soils 

 of those places which have been successful as breeding 

 stations always contain this hydrated silt in some propor- 

 tion or other, but not necessarily in such large quantities 

 as those places used as fattening stations. There is a 

 general similarity to be observed in good oyster soils from 

 various parts of the country. 



Their usual appearance is that of a loamy alluvial mud, 

 or calcareous plastic clay of a greyish-blue externally, but 

 which, when caked and broken open, appears intensely 

 black inside. Exposed to air, they oxydize rapidly, and 

 turn of an ochreous tint, and when dry they form a friable 

 mass. If washed, the materials of the rocks from which 

 they have been derived are readily discernible : spangles 

 of mica, felspar, and hornblende bespeaking an igneous 

 origin, as fragments of shell and particles of sand point to 

 the Eocene beds for their origin, whilst a preponderance 

 of Foraminifera and Globigerina indicate a cretaceous deri- 

 vation. 



In some places, as at Marennes, there is a shelly loam, 

 called in France sable vazal coquille, which possesses excel- 

 lent fattening properties. In Mesozoic times the Purbeck 

 beds must have been wonderful oyster grounds. The 

 influence of the soil upon both breeding and fattening, as 



(a) See Supplement. 



