SPONGES 61 
these filaments are composed of transparent, glass-like silica, the sponge ap- 
pears to be made of delicate lace work. This sponge occurs in the seas about 
Japan, and so singular is its structure, that it was for many years supposed to 
be an artificial product of the Japanese, See Fig. 34, where | have given a 
life-sized section of this sponge, 
pong 
Fig. 33. Fig. 34. 
A, portion of shell excavated 
by mining sponge. — B, fiber Section of Venus Flower Basket. 
of Gray Cup Sponge. 
WATER SYSTEM OF SPICULIGENOUS SPONGES. 
There is less sponge flesh on the skeletons of many living Spiculigenous 
Sponges than on those of the Horny Sponges, but this is somewhat variable, 
some, in the case of the common Branching Sponge of our coast (See page 35, 
B ) there is very little, while in some of the typical species, the sarcode is neay- 
ly or quite as abundant as in the Horny Sponges, 
