DETERIORATION OF AMERICAN OYSTER-BEDS. 149 



those dangers. Hence, as the embryo European oyster receives some 

 protection and the American none, it is inferred that the number of 

 American embryos in any community will be subjected to greater dan- 

 ger, and consequently it is probable that a larger number of eggs 

 and spermatozoa are provided, that the production may not be less. 

 If this is not the case, then the reproduction upon the European 

 beds is much greater than upon our own. Let us see if the inves- 

 tigations, conducted both in this country and abroad, support this 

 conclusion. 



Professor Mobius, in his work upon the oyster and oyster-culture, 

 estimates the number of eggs spawned by the European variety as 

 about 1,800,000, and his estimate is supported by Eyton, in his "His- 

 tory of the Oyster and Oyster-Fisheries." 



Professor Brooks estimates the possible number of eggs spawned 

 by the American variety to be as large as sixty millions, and the aver- 

 age number to be over nine millions, or the American oyster spawns 

 about nine times as many eggs as the European. The number of male 

 cells is so great that, even if it were possible, it would be unneces- 

 sary to estimate them ; but, from the comparison of the numbers of 

 eggs spawned, it will be seen that Nature supplies with the American 

 variety a much larger number of eggs, in order that the deficient 

 protection afforded them after fertilization may, as far as possible, be 

 remedied. 



It would seem that the growth of a bed and increase in the number 

 of oysters would be immense did we not know that the greater the 

 production of the germs in all forms of life the greater the mortality 

 among those germs ; and, therefore, any conclusions as to the impossi- 

 bility of destroying the fecundity of the oyster-beds, when such con- 

 clusions are based upon the large number of eggs spawned, must be 

 erroneous. The number of embryos surviving and maturing can not 

 be accurately stated for either variety, as we have but four data from 

 abroad bearing upon the question, and, until the last year, none at all 

 from this country. Professor Mobius has collected the results of the 

 official examinations of the Schleswig-Holstein beds, and from their 

 inspection has come to certain conclusions, and, as these results are 

 the only ones known to us, it may be interesting to briefly describe 

 the method of arriving at them. 



The observations were made on the beds by officials of the Govern- 

 ment from 1730 to 1852, and were conducted in the following manner : 

 Each bed was dredged over in three or six places, according to its 

 size, and the oysters taken were divided into three classes and care- 

 fully counted. The classes were denominated "marketable," "me- 

 dium," and "young growth." The "marketable" oysters were those 

 full-grown and mature, from seven to nine centimetres in length and 

 breadth, and eighteen millimetres thick. The " medium " were half- 

 grown oysters, from sixteen to eighteen millimetres thick, and less 



