(35) THE OYSTER AND OYSTER-CULTURE. 17 
In this similarity of proportions between the marketable and me- 
dium. oysters in different years and upon different beds a natural law 
is very Strikingly manifested. The medium-sized oysters of any bed 
consist of the descendants of the marketable ones. They are those 
members of the young broods which have escaped the numerous enemies 
living upon and around the beds, and which, despite the numerous 
attacks thade upon their lives, have grown into very respectable-sized 
animals. 
The medium oysters thus represent the total number of embryos from 
the bed which, in the struggle for existence, have continued to exist. 
A thousand mature oysters will produce during a breeding period, as I 
have already shown in chapter 2, at least 440,000,000 of young; but 
upon the beds alongside of these 1,000 mature oysters are to be found, 
on an average, not more than 421 half-grown ones; so that, aS a rule, 
for every Holstein oyster which is placed upon the table more than 
1,045,000 young are destroyed or die; and indeed even more-than this, 
for not only do those oysters which are over six years of age produce 
eggs, but those which are two and three years old also reproduce their 
kind to a certain extent. ‘The younger oysters, however, produce much 
less spawn than those which are mature, so I estimate that those half- 
grown oysters lying beside the mature ones on the same banks, and 
which are their offspring, will produce 60,000,000 young oysters. 
We thus have, upon a surface of oyster-bed occupied by 1,000 full- 
grown and 421 half-grown oysters, at least 500,000,000 of young pro- 
duced during the course of the summer, and of this immense number 
only 421 arrive at maturity. The immolation of a vast number of young 
germs is the means by which nature secures to a few germs the certainty 
of arriving at maturity. In order to render the ideas of germ-fecundity 
and productiveness more easily understood, I will make a comparison 
between the oyster and man. 
According to Wappiius,* for every 1,000 men there are 34.7 births. 
According to Bockh,t out of every 1,000 men born 554 arrive at maturity, 
that is, live to be twenty years or more of age; thus, on an average 34.7 
children are produced from 554 mature men, or 62.6 children from 1,000 
mature men. Since 1,000 full-grown oysters produce 440,000,000. of 
germs, then the germ-fecundity of the oyster is to the germ-fecundity of 
man as 440,000,000 to 62.6, or as 7,028,754 to 1. On the other hand, 
the number which arrive at maturity, is 579,002 times as great with 
mankind as with the oyster; for of 1,000 human embryos brought 
into the world 554 arrive at maturity, or of 440,000,000 newly born 
248,760,000 would live to grow up, while of 440,000,000 young oysters 
only 421 ever become capable of propagating their species. The pro- 
portion is then 421 to 243,760,000, or as 1 to 579,002. I am fully per- 
* Wappiius, Handbuch der Geographie und Statistik. Band I, 1855, Abth. I, p. 197. 
tR. Boéckh, Sterblichkeitstafel fiir den Preussischen Staat im Umfange von 1865, 
Jena, 1875. 
