54 
8 months although an individual oyster may only be in 
for one month or so. Eventually all the oysters not sold 
to éleveurs or exported get transferred from the ambu- 
lances to the other parts of the parc. 
Mons. Dasté told me that he soaked his ambulances 
thoroughly in coal tar once a year to preserve them. 
Although they are some little expense at first they last 
well, and are used over and over again. 
The rest of an oyster parc is marked out into certain 
areas like little rectangular fields having raised edges all 
round and a sluice at one corner so that the water may 
either be retained or allowed to run out (PI. I, fig. 6). At 
low water the boundary banks of these are all exposed but 
there is usually some 6 or 8 inches or so of water retained 
over the area. This shallow water becomes warm towards 
the last of the ebb and it is swarming with living things 
and so no doubt supphes abundance of food to the oysters 
lying on the floor of the enclosure. The banks bounding 
these areas are formed of two parallel rows of closely set 
vertical bunches of the local heath, Erica scoparia, with the 
space between, a foot or more wide, filled in with masses 
of a tenacious clay (Pl. I, fig. 6) obtained from the Ile 
des Oiseaux. In some places the boundary is strength- 
ened, or partly formed, of planks of wood and stakes. 
An objection which is urged against the use of the heath 
is that it forms a most attractive system of ‘‘ bouchots”’ 
upon which young mussels settle down and flourish. The 
mussels are not cultivated, nor desired, but they are present 
in considerable abundance over some parts of the oyster 
parcs, hanging in clusters from the branches of the heath. 
The men at Arcachon say that there is not enough hme 
in the water for both the oysters and the mussels, and 
that the latter being the stronger they get all the lime and 
the former suffer correspondingly. This is one way of ex- 
