18 REMARKS ON SOME CURIOUS SPONGES. 
intervening crust, of which Dr. Gray views the fascicle as 
the central axis. 
In some specimens of the Hyalonema fascicle the narrow 
end is enveloped in a spongy mass, or as Dr. Gray observes, 
"a species of sponge." He supposes the sponge to be inde- 
pendent of the fascicle or “coral,” though necessary to it 
as a means of attachment in its habitation. According to 
this view the fascicle with its warty crust, is a parasite of 
the sponge into which the fascicle is inserted. Dr. Gray 
remarks that *in general the specimens are withdrawn from 
. the spongy base and the lower part of the axis is cleaned ; 
but it is evident that they all are attached to such a sponge 
in their natural state." 
When the writer first had an opportunity of seeing a 
specimen of Hyalonema, consisting of a fascicle partially in- 
vested with a warty crust, presented to the Academy of Nat- 
ural Sciences of Philadelphia in 1860, and before he had 
seen an account of the remarkable production, his impression 
was that it was a silicious fascicle of a sponge, upon which 
a parasitie polyp had found a convenient and secure resting- 
place. M. Valenciennes had previously expressed a similar 
opinion, as observed in the introduction to Professor Milne 
Edwards’ work on British Fossil Corals. 
Notwithstanding the frequency of silicious threads enter- 
ing into the composition of many sponges, Dr. Gray re- 
marks, in referring the Hyalonema fascicle to a coral, that 
this is peculiar “as being the only body the animal nature of 
which is undoubted that is yet known to secrete silica; the 
spicules and axis of all the corals which had fallen under his 
observation being purely calcareous.” 
Professor Brandt of St. Petersburg views the fascicle and 
its warty crust as parts of a polyp, and the sponge mass as 
a parasite which attaches itself to the ein gradually pen- 
etrating its silicious axis, and finally killing 
Dr. Bowerbank who has so extensively ae the 
sponges in general, regards all three of the elements of the 
