SPONGES 67 
tions, for the incurrent orifices open through a fine net-work of fibers into a 
series of cells which radiate out quite regularly from the excurrent tubes. It 
occurs in abundance in rather deep water in Nassau Harbor. 
On page 42, Fig. 27,1 have also givena Spiculigenous Sponge, the 
Finger Sponge, (‘Tuba vaginalis Smitz.) This species varies from finger-like 
tubes, which have a smooth, or nearly smvoth exterior, ( See lower figure ) to 
tubes on which are developed thorn-lke processes. I have given a cut of the 
water system of this species on page 64, Fig. 36. This species has little sarcode. 
Another very remarkable sponge is the Creeping Sponge ( Smitza aulopo- 
ra ) which grows on the bottom, in remose branches, often two feet or more 
long. Although the excurrent openings are very apparent, (See Fig. 29, page 
44) the water system is made up of minute cells, and is very difficult to trace. 
The skeleton is made up of fine friable, mesh-like fibers which are be- 
set with fine spicules. ‘This is rather of a rare species, locally distributed in 
Bahama waters. 
Another minor group of the Spiculigenous Sponges, is the Mining Sponge. 
It is not uncommon to find on our New England Coast, shells of Mollusks 
which are pierced with holes (See Fig. 38, A, page 61, where I give -a small 
portion of one of these shells} These holes are made by a Mining Sponge 
when in its young stage. When older, it spreads outwards, often for several 
inches, and encloses small stones and other hard substances within its meshes. 
Another group of Silicious Sponges are the Incrusting Sponges belonging 
to the genus Terpios. These species spread over dead coral, stones and other 
objects in the sea, muchas lichens spread over stones, trees, shrubs etc. on the 
