304 Mr. n. J. Carter on the Species j Structure, and Animality 
bodies spherical, l-36th of an inch in diameter. Spicula of two 
kinds, large and small j large spicula smooth, slightly curved, 
pointed at each end, 1-5 7th of an inch long; small spicula 
smooth or thickly spiniferous, slightly curved or straight, l-200th 
of an inch long. Transparent portions of investing membrane 
abounding in the small spicula. 
3, Is of a light yellow colour, massive, spreading, convex, with 
short irregularly formed conical projections on the surface, or 
meandering ridges with sulci between them, attaining a thick- 
ness of two inches ; texture fine ; structure fibrous, plumose, ob- 
liquely reticulated towards the base, rectangularly reticulated 
towards the circumference; friable. Seed-like bodies spherical 
and l-40th of an inch in diameter. Spicula of two kinds, large 
and small; large spicula smooth, slightly curved, pointed at 
both ends, l-57th of an inch long; small spicula composed of 
a straight portion, sometimes slightly spiniferous, terminated at 
each end by a toothed disc with its points recurved or horizon- 
tal ; the central portion is l-400th of an inch long, the dkcs 
l-600th of an inch in diameter. 
4. Is of a bright yellow colour, massive, spreading, horizontal 
on the surface, with projecting, plumose, irregular portions, at- 
taining a thickness of about two inches ; texture coarse, loose ; 
structure fibrous, branched, plumose, obliquely reticulated ; semi- 
friable, may be compressed with the hand in water without under- 
going much injury. Seed-like bodies ovoid, l-28th of an inch 
in their long diameter, and 1-5 0th of an inch in their short 
diameter. Spicula of two kinds, large and small ; large spicula 
smooth, slightly curved, pointed at each end, l-66th of an inch 
long ; small spicula l-300th of an inch long ; consisting of a 
straight portion, terminated by a toothed disc at each end, with 
its points recurved or horizontal, l-950th of an inch in diameter. 
Transparent portions of investing membrane abounding in little 
siliceous stellated bodies, their arms projecting from a central 
cell, tapering to a point which ends in a stellated circle of re- 
curved spines ; they are l-600th part of an inch in diameter. 
The measurements of the seed-like bodies and the spicula are 
taken from the average size of the largest of their kind. 
Habitat . — On the inclined and under surfaces of rocks, or at- 
tached to floating bodies in the tanks of Bombay ; never at the 
bottom, and sometimes so high up as to be only covered by water 
three or four months in the year. 
Investing membrane . — The investing membrane of the Fresh- 
water Sponge, like the skin and the mucous membrane in the 
human body, is continuous throughout ; and, like a shut sac, 
surrounds the parenchymatous structure and spicular skeleton of 
the whole mass, without inclosing it. In some instances it 
