222 THE FISHERIES OF THE UNITED STATES. 



blue arctic ice. The observations were made at various liours of the day, sometimes in sunshine, sometimes under 

 a cloud, and at different stages of the tide. Thcj- are only to be taken as a mere indication of the general warmth 

 of the water on the surface of the beds in that region, in the autumn. It is worth mention that the fishermen 

 thought the water now about midway between its greatest cold and greatest warmth ; but I can hardly believe this 

 true. 



Table of temperatures (Fahrenheit). 



Degrees. 

 September 18, 1879, Shediac: Temperature of surface water ; ebbtide 61 



18 Temperature of air ; ebb tide '. 58 



19 Temperature of .air (raining) 54 



19 Temperature of shore water ; low tide 55 



19 Temperature of surface, J mile out in the bay 56 



19 Temperature of bottom, on oyster bed, 12 observations 58 



19, Point du Chene wharf : Bottom water, 2 fathoms f>7 



20, Summerside, Prince Edward island: Bottom water, 2 fathoms, ebb tide, 10 a. m 52^ 



20 Bottom water, 2 fathoms, incoming tide, 10 a. m 55 



20 Bottom water, 2 fathoms, high tide, 4 p. m 59 



20 Bottom water, 2 fathoms, tide going out, 5 p. m. , and deeper 



water 58 



21 Bottom water, deiid low tide, air chilly 56 



22, Richmond bay : Bottom water on bed, 4 p. m., ebbing tide 58 



However, I had no opportunity to learn the minimum temperature which these oysters would survive. It 

 would not be safe to say that the sole reason why oysters did not grow off Port Hood, for instance, was that the 

 bottom water was as cold as 40° or 42c> Fahr. There are probably various other reasons. I was told by fishermen 

 on the island, and at Shediac, that they did not think the water could be too cold, short of actual freezing. They 

 were united in the opinion, however, that ice had been the direct cause of the extinction of many of the beds. As 

 I have said in my chapter descriptive of that district, however, I am sure that ice, or nature at large, has had less 

 to do with this misfortune than the heedless greed of the oystermen themselves. 



Food of the oystek. — The question of proper and sufScient food is also one of great importance, in considering 

 the question of oyster- growth, whether in natural or artificial beds. The anatomical arrangement of the oyster's 

 mouth and stomach, have already been explained, and the general character of his miscroscopic, floating food 

 alluded to. Some furthei details in respect to this may be of importance. In a paper pulilislied in the report to 

 the British government on oyster-culture in Ireland, in 1870, Prof. W. K. Sullivan, of Dublin, remarked, that 

 independently of the mechanical constitution of the shore and littoral sea-bottom, i. e., deposition of sediment, the 

 currents, the temperature, etc., tlie nature of the soil produces a marked influence upon the food of the plants and 

 sedentary animals that inhabit the locality, as well as upon the association of species. Especially is it the case 

 with oysters, that the soil exerts so much influence on the shape, size, color, brittleness of shell, and flavor of the 

 meat, that an experienced person can tell with great certainty where any i)articular specimen was grown. "Were 

 we able to determine the specific qualities of the soil which produce those diiferences in the qualities of oysters, it 

 would be an important step in their cultivation. Again, soils favorable for the reproduction of the oyster are not 

 always equally favorable for their subsequent development; and, again, there are many places where oysters thrive 

 but where they cannot breed. This 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 suflicient 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. * * * j believe the character and abundance of Diatomacea and Ehisojwda, and other microscopic 

 animals, in oyster-grounds, is of primary im])ortance in connection with oyster cultivation. The green color 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 maiuly u])on the nature and comjiarative abundance of the Diatomacea, Rhizopoda, Infusoria, and other 

 microscopical organisms which inhabit the ground. I have accordingly always noted where the mud appeai-ed to 

 be rich in Diatomacea, Foraminifera, and other microscopic 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 comiietent microscopist, acquainted with the classes of plants and animals just mentioned, would be of great 

 scientific interest and i)ractical importance." 



Of all the edible matter afloat in the water where the oyster lives, probably none is of greater importance to 

 this and other moUusks than the Diatoms — microscopic forms of aquatic plants which, in almost infinite variety, 

 swarm in both salt and fresh water, in the pond and ditch, in river and estuary, and throughout the open ocean. 

 The distinguishing feature of the Diatoms is their indestructible skeleton of flint, iu the shape of a pair of 



