[61] ' OYSTER CULTURE. 813 
centimeters in depth and remain dry for many hours. Hence there are 
diverse conditions of life for the animals which inhabit these different 
zones, and there results the necessity of constructing the crawls or pali- 
sades in series along the slope of the shore so that the sea will visit them 
less and less in proportion as they approach the inner limits of the water. 
The fishermen of Aiguillon call those crawls which are farthest out in the 
sea, and which are uncovered only by the lowest tides, low crawls ; the 
two next inner rows are called false crawls, and those nearest the land, 
and consequently uncovered most frequently, high crawls. The outer line 
is generally formed of single posts (Fig. 20), without any wicker-work 
whatever, and the posts are : 
somewhat nearer together = — =. 
than in the line of palisades. = —— 
They serve especially as col- £ : == 
lectors of the young growth. 
In fact, at the spawning pe- 
riod they arrest, in the zone 
in which they are planted, = 
the young which are being 
swept out by the tide, and = 
offer to them, owing to their = 
nearly continuous immer- = 
sion, a more secure and ap- 
propriate protection than the 
other collectors, where they 
would frequently be left out 
of water. 
The fishermen thus resort 
to these outer posts for the 
seed necessary to supply the false crawls. Toobtain this the workmen go 
about the monthof July, at the beginning of the spring-tide, to detach the 
young, which are about the size of a bean, having been spawned in Feb- 
ruary and March. They are detached from the posts, in bunches, by 
means of a hook-shaped instrument, and are gathered into baskets and 
transported in the small foot-boats to the false palisades, to which they are 
then attached. In attaching them, the bunches, formed by the adherence 
of the byssus to the shells, are inclosed one by one in a bourse of old 
twine and then tied in the interstices of the wicker-work, being equally 
distributed, so that nothing shall interfere with their future development. 
Soon the net which incloses the mussels disappears, but it has become 
useless, the mussels being by this time firmly attached by their byssus 
to the branches of the wicker-work. Ina short time, by a continuous 
and rapid growth, the mussels cover the entire palisade or trellis in a 
dense layer of clusters, in which one can scarcely find a vacant space 
(Fig. 21). When, finally, this increase in size threatens their further 
development, they are detached, and transferred to palisades still nearer 
Fic. 20.—Low crawls. (Bouchots d’aval.) 
