A PRACTICAL METHOD OF SPONGE CULTURE. 579 
develop a smooth, soft, and very durable felt-like surface. These sponges cost 
more to grow than those of ordinary shape, but experiments recently inaugurated 
will probably make the additional cost of production trifling. The superior 
durability of sponges grown in this manner should make it possible to market 
them at a price considerably above that brought by the natural product. 
It has been found that the sponges grown suspended above the bottom are 
superior in density and closeness of fiber to the natural sponges from the same 
locality. The same superiority is not apparent in those grown on disks, but 
the absence of the torn surface or root which characterizes the natural product 
makes them much more durable than the latter, the close felting of the attached 
surface making it the softest and strongest part of the sponge. In other words, 
the place of greatest weakness is converted into that of greatest strength, while 
the other parts remain normal. The artificially grown specimens are always 
superior to the natural product of the same immediate locality. 
At Anclote Key a considerable proportion of the sponges grown on the 
bottom are affected with so-called crab holes, cavities which commonly contain 
small crabs. The general opinion of the spongers is that the crustaceans pro- 
duce the holes, but of this I am by no means assured. As has been explained 
heretofore in this paper, practically all of the sponges planted on the bottom 
in this locality were previously injured by fresh water and already bore patches 
of dead tissue when planted on the bottom. As these dead areas sloughed away 
they left cavities, and I believe that these invited the crabs, which thus did not 
actually excavate their hiding places. In the many hundreds of these crab 
holes which I have examined in both artificially and naturally grown spenges 
I have never seen the slightest indication of a raw surface which looked as if 
the crab had torn away the tissues of the sponge. The presence of the crab, 
however, undoubtedly prevents the hole from filling up as it would tend to do 
under other conditions. In none of the healthy sponges planted on the bottom 
in Biscayne Bay do these holes occur, though they are found in the usual pro- 
portion in the natural sponges of the vicinity. 
HARVESTING. 
With the wire method of suspension from stakes, if such can be com- 
mercially developed, the problem of gathering the crop is simplified, for all 
that is necessary is to detach the wire at one end and slide the sponges off. 
As has been shown in the foregoing, however, this method has not yet been 
perfected and can hardly be commercially considered as yet. 
With bottom planting on disks or spindles the method of harvesting will 
vary with the depth of water. In comparatively shallow water the crop can 
be taken up when matured by means of hooks, and the conditions essential are 
