432 BULLETIN OF THE BUREAU OF FISHERIES. 
and found the density gradually falling from about 1.0205 on the sponge grounds 
at either end to about 1.0135 approximately midway between. All other con- 
ditions for the maintenance of sponge life appear to be present, and certain 
species, like the loggerhead, more tolerant of fresh water, are found in abundance. 
In the construction of the new line of railroad to Key West many of the 
passes between the keys west of Key Largo have been completely or partially 
closed and it is not improbable that the salinity of the water will be so lowered 
as to affect adversely the sponge grounds near the Matecumbes. 
The Key grounds produce sponges in greater variety than the Bay grounds. 
Not only are there more noncommercial species but there are more useful kinds, 
and of each of these there are a number of local varieties readily recognized 
by the spongers and dealers. All have, however, one well-marked character- 
istic that in general serves to distinguish them from corresponding species 
taken ‘‘up the bay,’”’ namely, a reddish or rusty appearance of the interior 
fibers, called ‘“‘red root”? on account of its being more readily seen on that 
portion of the sponge torn away from its attachment to the bottom. ‘This 
color is not generally exhibited by the strictly peripheral fibers, but is readily 
observable in the oscula and at the bottoms of the channels or grooves which 
traverse the surface, and upon cutting the sponge it is found to permeate the 
whole interior. It is due to an oxide of iron and is popularly supposed among 
those engaged in the business to be caused in some manner by the coral rocks 
to which the key sponges are commonly attached. That it is due to the con- 
stituency of the water among the keys there can be no doubt, but that it is 
not absorbed directly from the rocks is shown by its presence in sponges growing 
above the bottom attached to sea feathers (gorgonians) or artificially grown 
from cuttings attached to suspended wires. Red-rooted sponges are almost 
invariably more tender, weaker in fiber, and less durable than those of gener- 
ally similar texture not so colored, but whether the coloring material causes 
the weakness or whether the conditions producing the two are merely coinci- 
dent can not be stated. The color is quite different from the paler yellow 
seen in some of the Bay sponges. 
The “barry bottom” of the Key grounds is generally fairly level as to 
surface, though on the reefs and in places on the Key shore of the Hawk Channel 
there are bowlders and heads of coral rock, often rising from a depth of 2 or 3 
fathoms almost or quite to the surface. The commercial species found on the 
Key grounds are sheepswool, yellow, velvet or boat, grass, and glove. The 
velvet or boat sponge is obtained principally from the reefs and owing to the 
difficulty of working in that exposed region is to be had in but comparatively 
small quantities. The other species are generally distributed. 
The Key grounds are subdivided into innumerable more or less poorly 
defined areas, each of which has received from the spongers one or more local 
