SPONGES 59 
given are enlarged about ten diameters excepting when they are given as be- 
ing otherwise. | 
It is instructive tonote that when growing twigs'come in contact with 
the rocky surface upon which the sponge grows, they become arrested sud- 
denly in a similar manner as when they come in contact with the lining mem- 
brane of the central tube. (See Fig. 17, E, where I give a cut of three of these 
arrested growths. ) 
OTHER HORNY SPONGES. 
Although the sponges given below are of no known commercial value, yet 
they are of great scientific importance, and a study of the type forms given will 
greatly aid the student in acquiring a knowledge of the sponges. 
One of the most common Horny Sponges of.the Bahama and Florida 
waters, is the Logger-head Sponge, one of the Goat Sponges ( Genus Hircinea ) 
all of which are characterized by their strong disagreeable odor, which bears a 
somewhat fanciful resemblance to the odor emitted by goats, but to my mind 
they smell strongly of phosphorous. (See remarks under the Odor of Horny 
Sponges ) . 
The color of sponges of this genus varies from greenish gray to gray and 
black. ‘They live in comparatively shallow water, often on banks where they 
are exposed to the falling tide. 
The skeleton is coarse, the fibers being flattened, aad appear to be tied to- 
gether in bundles which, when growing, project beyond the surface. ( See Fig. 
18, where I give the cut ofa Logger-head Sponge, a typical species of a flat- 
tened spherical form, which often becomes two or three feet in diameter. Large 
specimens are attached so strongly to the bottom that they are torn away with 
great difficulty. This is a very common species. 
