Page:Popular Science Monthly Volume 20.djvu/161

Rh 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 danger, 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 investigations, conducted both in this country and abroad, support this conclusion.

Professor Möbius, 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 "History 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 average 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 unnecessary 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 impossibility of destroying the fecundity of the oyster-beds, when such conclusions 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 Möbius 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 Government 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 carefully counted. The classes were denominated "marketable," "medium," 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