[11] OYSTER CULTURE. 7163 
after by certain amateurs; but this should not be done, for when in this 
condition the animal should be especially protected. Although we may 
now consider the eggs as laid, yet they will not be ready for some time 
to leave the protecting mantle of the mother; they must undergo a sort 
of incubation, during which the mass loses some of its fluidity, and as- 
sumes a dark, violet color, a certain indication of maturity. From this 
time the embryos can lead an independent existence, and if they are now 
taken from the mantle they can be preserved alive for several days in 
sea-water; and, moreover, by frequently renewing this water and arrang- 
ing solid bodies for their attachment, such as bits of wood or fragments 
of shells, one can reproduce artificially what takes place at every spawn- 
ing season in the depths of the ocean. When the embryonic mass has 
assumed a bluish black or muddy color, the 
young leave the mantle of the mother and 
become dispersed in the surrounding waters. 
Each individual is furnished, at this time, 
with a special swimming organ, which disap- 
pears as soon as the animal has found a suit- 
able place of attachment where it can con- 
tinue its growth. This fleshy pad, or velum, 
is covered with cilia, and by the aid of these 
and of powerful muscles, which seem to re- 
tract or extend the velum, the embryo can 
move in any direction. 
The accompanying figures represent much 
enlarged a young oyster which has just left 
the mantle-cavity of the mother oyster; the 
first shows it in front view; the second, as 
seen in profile; at the upper part can be seen 
the ciliated velum. The number of embryos 
spawned in a single year from a single ma- 
ture oyster cannot be estimated at less than 
from one to two millions, and the imagina-  yy¢.3 Embryo Arno Caeeiindeh 
tion is simply astounded at the idea of the ©™rsed). 
immense numbers which would result from each annual spawning of a 
single bed of oysters, if this living cloud, which at a given moment 
almost darkens the waters, found for each one of the minute beings com- 
posing it a support and a protection which would enable it to escape 
the innumerable causes of destruction to which the laws of nature 
and human negligence expose them, and develop into mature and edi- 
ble oysters. In order that an embryo oyster may live to acquire a shell 
which shall serve to protect it, it is necessary that it should find near at 
hand a solid body, stone, bit of wood, or shell, for its attachment, so 
that it may be protected from too strong currents, which would carry 
it off; from deposits of mud, which would smother it; and from the 
voracity of the inhabitants of the sea, among which there are countless 
