THE COMMERCIAL SPONGES AND THE SPONGE FISHERIES. 501 
less operative with the divers; but it is equally beyond doubt that no incon- 
siderable proportion are derived from sponges in deeper water, at a distance 
from the beds on which the young finally settle. 
We have evidence that this must be true in the phenomena of the recupera- 
tion of large areas after the practically complete extermination of the sponges 
from so-called ‘‘ poison water.’’ This has recurred at irregular intervals about 
ten years apart. In 1878, for instance, practically all sponges accessible to the 
hookers between Johns Pass and Cedar Keys were destroyed and the fishery was 
abandoned for several years, the first sign of recuperation being observed about 
1882. About 1895 a similar occurrence in the northern part of the Bay grounds 
killed the sponges between St. Marks and the mouth of the Suwanee River from 
about the 5-fathom curve to the greatest depth explored by the hookers, and in 
1gor I was informed that the first sponges taken since then from the depleted 
bed had been obtained recently. 
The evidence all indicates that over the large areas involved few if any 
sponges escaped the disaster, and as the repopulation of the beds was apparent 
practically simultaneously over the whole area and did not appear first merely 
at its edges, it is evident that the young must have been derived from grounds 
more or less remote. The very young sponge is a free-swimming organism which 
is probably often carried far by currents before it reaches the stage at which 
it settles down and becomes fixed. It is evident that the rate or probability of 
recuperation of any exhausted area depends not only on the number of resident 
breeding sponges, but also upon the presence and number of such sponges on 
surrounding areas. An exhausted area adjacent to virgin beds will have a more 
abundant set of young than if the surrounding areas are equally exhausted. In 
the history of the sponge grounds of the Gulf of Mexico prior to 1905 there were 
always untouched bars offshore just beyond reach of the hooks, and these must 
have supplied untold millions of fry to the workable beds, retarding their com- 
mercial exhaustion. This condition is now changing, for the offshore beds them- 
selves are yielding/up their sponges in large numbers, and even if they exist in 
still deeper water than has been explored the virgin beds are becoming more 
and more remote from inshore waters. It would appear, then, though the basis 
of the conclusion is purely a priori, that, in view of the increasing exploitation 
of the deeper beds, the grounds now reserved to the hookers will probably not 
have the same powers of recuperation in the future as in the past, and that with 
the same expenditure of effort in the fishery the product of these beds will tend 
to fall at an increasing rate. The consequence of this will be that the principal 
seat of the sponge fishery will gradually move into deeper and deeper water 
until the limit is reached, either by the depth in which it proves practicable to 
work or by the attainment of the limits of sponge production, which may be 
fixed by either the depth of water or the absence of suitable bottom. 
