732 NATURAL HISTORY OF AQUATIC ANIMALS. 



food has less chance to multiply. If the French mode applies successfully to an inferior species, 

 ours, which grows so much more rapidly, ought to derive a proportionally greater benefit from 

 being treated in the same manner. However, before we are ready to deal with the material 

 on which the Oyster feeds, we desire a more perfect acquaintance with the microscopic life 

 which grows upon oyster-beds and swims about in the adjacent waters. From the fact that 

 the lower forms of life in fresh water often appear in great abundance one year, while in the 

 next, from some unexplained cause, none of the same species will be found in the same situation, 

 we may conclude that similar seasonal variations occur in the phases of the microscopic life of 

 a given oyster-bed and its vicinity. 



Inpltjenobs op environment. — Such yearly variations in the abundance of microscopic 

 life are probably the causes of the variable condition of t he Oysters taken from the same beds 

 during the same season of different years. Violent or sudden changes of temperature are prob- 

 ably often the cause of the destruction of a great amount of the minute life upon which the Oyster 

 feeds. Backward and stormy seasons doubtless also aff'ect the abundance of the microscopic life 

 of the sea. All of these questions have, however, as yet been scarcely touched, and, judging from 

 the disposition of many of our students of zoology to be content merely with a description of new 

 species and the compilation of Usts, instead of also entering into investigations of the life-histories, 

 the relative abundance of individuals, and the influence of surrounding conditions upon the 

 forms they study, it will take some time yet before we get the information so much desired. 

 When we arrive at this knowledge we will know why it is that Oysters taken from a certain bed 

 are in good condition for a season or two and then for one or more years are found to be watery and 

 of poor quality, as well as why it is that the Oysters of certain beds, which for years have had a 

 high reputation for their fine qualities, are suddenly found to be more or less green in the beard, 

 as I have been informed is now the case with the Oysters of Lynn Haven Bay, Virginia. 



As to the influence of brackish water in improving the condition of Oysters, let me observe 

 here tliat those who hold to that opinion appear to forget to bear in mind that brackish- water beds 

 are often in the case just described ; that lying in shallow, relatively quiet water, an abundance 

 of food is generated which is rapidly consumed by the animal?, quickly bringing the latter into 

 condition, the brackish state of the water getting the credit of the result. 



" In a paper published 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 constitu- 

 tion of the shore and littoral sea-bottom, i. e., deposition of sediment, the currents, the temperature, 

 etc., the 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 

 particular specimen was grown. ^ . . . Were we able to determine the specific qualities of 

 the soil which produce those differences 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 that of the other causes enumerated ; and next, because, though 

 much has been written on the subject of Oysters, 1 do not know of any systematic series of experi- 



^E. Ikgkrsoll: Eeport on Oyster Industry, Tenth Census. 



