SPONGES 69 
inroads of internal parasites, and to ensure them against the attacks of para- 
sitical sponges of all kinds. Some species of Spiculigenous Sponges have the 
spicules so well developed that they are exceedingly disagreeable to handle, 
There is, for example, a species which grows between tide marks in Nassau 
Harbor, which is almost wholly made up of slender spicules which project 
from the surface. (See Fig. 39) When these sponges are handled ever so 
lightly, the points of the spicules enter the flesh and break off there, and after 
a time produce a burning sensation, and the skin of the hands, especially be- 
tween the fingers, becomes.red and inflamed, exactly as if the spicules contained 
some poison, in other words, the irritation produced by them is more than 
would be produced by the presence of thorns, or better, the prickles which 
erow in clusters on the fruit of the cactus, known as the prickly pear. 
In regard to the habits of particular species of Silicious Sponges which 
occur in the sea, I give the following account of some of the typical species as 
Lhave observed them. 
Scarlet Sponge. ‘This beautiful and striking species grows on banks, usu- 
ally embedded in mud, with no particular basal attachment for any hard object. 
But as the substance.of the sponge is soft and easily injured, we generally find 
that the sponge avails itselfof the support afforded by a branching species of 
nullipore and broken seaweed and other debris. See Fig. 19 where the nul- 
ipores etc. may be seen projecting from the base. Another support which 
we frequently find in this sponge is a species of living worm shell, which 
