THE COMMERCIAL SPONGES AND THE SPONGE FISHERIES. 407 
Commercial sponges are very susceptible to the influences of environment, 
and when transplanted from one place to another speedily change in character. 
If grown in the midst of vegetation they become coarse and open in texture, of 
irregular shape, with long superficial processes and protruding oscular tubes. 
If raised high above the bottom the texture becomes more dense than that of 
neighboring bottom-grown specimens. Individuals suspended artificially on 
wires or growing naturally on gorgonians (sea feathers) tend to become spherical, 
and those torn loose to roll freely over the bottom assume the same shape, but 
develop harsh, very tough surfaces. 
The commercial sponges of Florida, especially the sheepswool, yellow, and 
velvet sponges, can not live in water which falls for any considerable period 
much below oceanic salinity. Observations made in connection with sponge 
culture and on the natural beds indicate that the allowable minimum of salinity 
is reached when the water falls to a specific gravity of about 1.019 or 1.020. 
Exposure to the air is tolerated for considerable periods, especially during cool 
weather, and sponges grow naturally in situations where they are occasionally 
bared at low tide. From this extremely shallow water, the distribution of com- 
mercial sponges in Florida extends certainly to depths of 110 feet and probably 
to much deeper water, as in the Mediterranean, where they range to a depth of 
500 to 600 feet. Of the food of sponges practically nothing is known. That it is 
taken in through the canal system and that it must be in a finely divided state 
is practically certain, but of what it consists and by what tissues it is absorbed 
is unknown. ‘The so-called ‘“‘roots’’ of sponges perform no other purpose than 
that of anchorage and are not special organs of nutrition like the roots of plants. 
There appear to be few, if any, important natural enemies of commercial 
sponges, though perhaps they are subject to the attacks of microscopic organ- 
isms, producing certain epidemics which are ordinarily attributed to other 
causes. Crabs are ofter found in cavities burrowed in their substance, but despite 
popular belief to the contrary, I do not think that the chambers are actually 
excavated by the crabs. They probably find them ready-made and when they 
crawl in the pressure of their shells prevents filling up, or possibly expands the 
cavity. 
Il. REQUISITES OF A COMMERCIAL SPONGE. 
The qualities of the skeleton affecting the commercial value of sponges are 
color, size and shape, softness, fineness, durability, resiliency, and absorptiveness. 
Color.—The color is the consideration of least intrinsic importance, though 
for purely esthetic reasons it exerts a considerable influence on the price. The 
most desired color varies somewhat with different classes of sponges, but in 
general the lighter tones are preferred. For bath purposes a pale yellow appears 
to be most in demand, and this requirement is catered to by various processes 
