4G SPONGES 
yellow color. They usually prefer rocks slightly elevated above the bottom, 
but in some cases they grew directly on the bottom where they were surround- 
ed by sand. When brought to the surface and exposed to the air they almost 
imediately begin to blacken, beginning to change color, first where they were 
bruised, even ever soslightly, then the dark hues spread rapidly over the en- 
tire sponge. When handled, the mucous-like substance which exuded from 
them also oxodized and stained the hands black. 
Fig. 31. 
A, spicules of Fresh Water A, spicules of Salt Water Sponges : 
Sponge ; B, ova of same. P, spicules of Fresh Water Sponges. 
Upon the closest examination, I could not perceive the slightest shrinking 
nor any contraction of the sarcode, nur any changes whatever in the diameter of 
the orifice in the middle of the closing membiane of the cential tuke. 
We also procured a quantity of these sponges at Allen’s Harbor, about 
three miles north of Highburn Key, all growing in comparatively sheltered 
situations, as at Highburn Key; that is never directly in swift tide ways, but 
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