SPONGES 43 
head Sponge as to become almost overpowering when one is handleing a fresh- 
ly gathered specimen, and the peeuliér phosphorous smell remains upon the 
hands for hours. So strong is this odor that it suggests that possibly the spong- 
es which emit 1f may be of some commercial value on account of the phospho- 
rus which must be continued within their tissues. 
An exception to the rule that sponges emita disagreeable odor, may be 
found in the Violet Sponge: asponge, which although yellow in life, rapidly 
changes in drying to a bright violet. In this species the odor is not at all un- 
pleasant. 
HABITS OF HORNY SPONGES. 
Horny Sponges occur in all depths of water from between tide marks to 
forty or fifty feet deep. Among the commercial species, the Reef Sponge grows 
in the shallowest water, seldom being found at a greater depth than four feet. 
while I have often found them exposed by the falling tide. The best of the 
commercial species are found in about thirty feet of water. A few of the Hor- 
hy Speages grow upon mud or sand banks, but the majority of the species 
are found en rocky bars, here, in the great depths, below ordinary wave distur- 
bance, amid corals and waving gorgonias, these singular organisms thrive 
vest. 
Asa rule, sponges do not display any great sensitiveness upon being 
handled, but the Hollow-fibered Sponge, Dendrospongia crassa, shrinks very 
much upon being touched, completely closing the large excurrent tubes, that 
even if they were an inch in diameter before the animal was disturbed, 
beceme wholly indistinguishable in the mass of the sponge, nor will they open 
again for an hour or more. . Ifa sponge of this species be cut away from the 
