[3] OYSTER AND MUSSEL INDUSTRIES. 827 
are suspended bunches of brushwood intended to increase the growing 
individuals which are awaiting collection. 
In the spawning season, which is ordinarily from June to the end of 
September, the oysters lay their eggs; but they do not abandon them, 
as happens with a great number of marine animals. They protect them 
during incubation in the folds of the mantle, between the gills. There 
they remain immersed in a mucous substance, necessary to their evolu- 
tion, and in the midst of which they acquire their embryonic development. 
The mass of eggs resembles thick cream in color and consistency; and 
moreover, the oysters at this time, owing to their appearance are called, 
milky oysters (huitres laiteuses). But the whitish tint so characteristic of 
the eggs when first deposited assumes little by little, as the process of 
development advances, a shade of clear yellow, then of dark yellow, 
changing by degeneration into a brownish gray, or a very decided violet 
gray. The entire mass, which, at the same time, loses its fluidity, prob- 
ably in consequence of the progressive reabsorption of the mucous sub- 
stance enveloping the eggs, presents then the appearance of compact 
mud. This stage indicates that the development has reached its limit, 
and is a sign of the approaching expulsion of the embryos and of their 
independent existence; for, already, they thrive very well without the 
protection furnished by the maternal organs.* 
The mother soon ejects the young ones hatched in her mantle. They 
go forth furnished with a temporary apparatus for swimming, which 
enables them to seek a fixed body to which they may attach themselves. 
This apparatus, discovered by Dr. Davaine, and described in the remark- 
able work which he has undertaken and executed under the auspices 
of M. Rayer, my associate in the Academy of Sciences, consists of a 
sort of ciliated cushion, provided with powerful muscles, by the aid of 
which the animal can at will protrude the cushion from the valves or 
retract it. When the young oyster has become attached, this cushion, 
which is henceforth useless, is lost, or, as is more usual, atrophies in posi- 
tion and disappears by degrees. 
*It would be interesting, especially in a commercial point of view, to know whether 
embryos which have arrived at this stage of development, and which have been 
placed in a pond, or recess of the sea previously prepared, would survive this prema- 
ture and forced hatching, attach themselves, and continue to grow. An experiment, 
incomplete it is true, but which I propose to enlarge upon, would seem to show that 
their organization is sufficiently perfect to permit them to be born prematurely, and, if 
I may be allowed the expression, outside of the medium in which their cyolution is 
accomplished. Thus, young oysters extracted from the mantle of the mother, and 
placed in a little vessel filled with sea-water, still preserved all their activity at the 
end of the fourth day; 24 hours later some were motionless; the sixth day all were 
dead. In fact, the water of the vessel had not been renewed, and had acquired too 
great a percentage of salt, and too high a temperature, which very probably hastened 
their death. I am led to believe that under other circumstances, care being taken 
to change the liquid of the vessel every day, this experiment would give results which 
one would be able, perhaps, to apply to the indusiry. 
