LE “OVSTER. 201 
number of 10,000,000! However, more modern naturalists consider 
the limit to be about 2,000,000—a number almost incredibly large. 
The eggs are yellow; they are hatched in the mantle, and when 
the embryo leaves the parent it can breathe. The spawning time 
is usually from June to September. During the period of incuba- 
tion the eggs are enveloped in a mucous matter, which is necessary 
to their development; it has very much the appearance of cream, 
but as the period of gestation proceeds, this mucous material 
changes its colour, gradually becoming darker. An experienced 
eye, from the colour of the mucus, can pronounce the stage which 
the embryos have reached. 
The oyster differs from most shell-fish, in that its young do 
not leave the folds of the mantle until they are capable of living 
YOUNG OYSTERS, WITH THEIR NATATORY CILS. 
without the maternal protection. Almost all shell-fish throw out 
their ova, committing them, and the protection of the young, to 
circumstances. An oyster-bank, in the spawning season, is a most 
interesting place—every oyster is throwing out a whole nation of 
descendants, filling the water with living dust; so that, frequently, 
the sea is clouded by the sfaz, as the young oysters are termed. 
The microscope reveals to us that the young oyster has a per- 
fect shell, and is also furnished with vibratory cils, which enable 
it to swim. When the current carries it against any solid body it 
immediately adheres, the cils disappear, and the oyster begins 
to develop; in three years it reaches its full growth. Before it 
settles down in life it swims about the neighbourhood of the 
mother; and, we are told, that at any alarm, it again seeks refuge 
within the maternal shell. This prolific production might well be 
supposed to be a sure means of the rapid propagation of these 
