13 
The number of male cells which a single male will yield is* 
great beyond all power of expression, but the number of eggs 
which an average female will furnish may be estimated with 
sufficient exactness. A single ripe egg measures about one 
five hundredth of an inch in diameter, or five hundred laid in a 
row, touching each other, would make one inch ; and a square 
inch would contain five hundred such rows, or 500 x 500 =■ 
250,000 eggs. Nearly all the eggs of a perfectly ripe female 
may be washed out of the ovary into a beaker of sea water, 
and as they are heavier than the sea water, they soon sink to 
the bottom, and the eggs of a medium sized female will cover 
the bottom of a beaker two inches in diameter with a layer 
of eggs one-twentieth of an inch deep. The area of the bot- 
tom of a beaker two inches in diameter is a little more than 
three square inches, and a layer of eggs one-twentieth of an 
inch deep, covering three square inches, is equal to one three- 
twentieths of an inch deep and two square, and as a single layer 
of eggs is one-five-hundredth of an inch thick, a layer three- 
twentieths of an inch thick will contain seventy-five layers of 
eggs, with 250,000 eggs in each layer, or 18,750,000 eggs. It 
is difficult to get the eggs perfectly pure, and if we allow one- 
half for foreign matter and errors of measurement, and for 
imperfect contact between the eggs, we shall have more than 
nine millions as the number of eggs laid by an oyster of av- 
erage size, a number which is probably less than the true 
number. 
Mobius estimates the number of eggs laid by an average 
European oyster at 1,012,925, or only one-ninth the num- 
ber laid by an ordinary American oyster, but the Ameri- 
can oyster is very much larger than the European, while its 
eggs are less than one-third as large, so the want of agree- 
ment between these estimates does not indicate that either of 
them is incorrect.* Another estimate of the number of eggs 
*Mobius’ measurement, from .15 to .18 millimeters, is given (Austern und 
Austern-wirtschaft, 1877), as the diameter, not of the egg, but of the em- 
bryo, but his figures show that the European oyster, like the American, 
does not grow much during the early stages of development, but remains of 
about the same size as the egg. 
