ON ACEPHALA. 375 
and from which it may be suffered to run out. In general, 
these excavations, which are in the form of parallelograms, 
are only a few feet in depth, and their walls are sloping. 
They communicate with the sea by means of a canal, more or 
less long, and furnished with a small flood-gate. When the 
water is to be changed, the flood-gate is opened at the end of 
the low tide, and the reservoir is filled at high water. The 
bottom and sides of these passes are covered with pebbles, or 
very coarse sand, for mud must be carefully avoided, which is 
always very hurtful to oysters. Care must also be taken that 
the motion of the water be not considerable enough to cause 
any grains of sand to enter the shells. When the park is thus 
disposed, the oysters are placed there in their natural position, 
that is, horizontally, the gibbous valve underneath, on a part 
of the elevation of the slope, so deep, that it will be difficult 
for robbers to get at them, but not too deep, that we may avoid 
as much as possible the deposition of the mud. The more 
suitably the oysters are fixed, the more cautiously they are 
moved, and the more the deposition of mud is prevented, 
which may be done by washing the walls of the park, and 
frequently throwing water on the oysters, when left uncovered, 
the sooner will these animals become good and marketable. 
Those also which happen to be dead should be carefully 
thrown away, and they are easily recognized, as they remain 
half open when the water has retired. There are some doubts 
as to the preference which should be given to these parks, or 
depots, according as the water which they contain is received 
every tide, or only twice a month. In the first case the 
oyster may be, perhaps, a little harder, and more coriaceous 
that in the second. But the water should always be very 
clear and limpid. 
Fresh water is not good for oysters, at least when the 
quantity which is introduced into the parks, either by great 
rains or inundations, becomes too considerable. Experience 
