1114 
DE. J. S. BOWEEBANK ON THE ANATOMY 
Zoological Society of London for 1857, page 279.) This description applies only to the 
singular cloacal appendages to the sponge from amidst which it springs, the structure 
of the body of the animal being evidently considered by the author as an extraneous 
mass. The basal sponge is undoubtedly a portion of the animal to which the part 
described by Dr. Gray belongs, the spicula of the elongated cloacal portion being also 
abundant in the basal mass of sponge ; and the basal mass of the specimen described by 
Dr. Gray is identical in its structural character with that of the specimen of Hyalonema 
miraVdis in the Bristol Museum. It becomes necessary therefore to remodel the generic 
characters so as to embrace the leading distinctive structures of the skeleton of the 
animal ; and I propose the following form of description : — 
Skeleton an indefinite network of siliceous spicula, composed of separated elongated 
fasciculi reposing on continuous membranes, having the middle of the sponge 
perforated vertically by an extended spiral fasciculus of single, elongated and very 
large spicula, forming the axial skeleton of a columnar cloacal system. 
The construction of the skeleton of the mass of the sponge is intermediate between 
that of Halichondria panicea and Ilymeniacidon caruncula, the respective types of those 
genera. The network of fasciculated spicula appears never to be definite and continuous 
as in the former, nor are the skeleton-spicula in a dispersed condition on the continuous 
membranes as in the latter, but are gathered into elongated fasciculi which cross each 
other in the same plane in every imaginable direction, but without ever appearing to 
anastomose. The fasciculi vary exceedingly in the number of spicula of which their 
diameter is formed, sometimes consisting of two or three spicula only, and at other times 
of more than it is possible to count. They often divide, the branches passing in different 
directions, but they never reunite or anastomose with other fasciculi. A portion of 
this network of spicula is represented by figure 3, Plate XXXI. Part 11. The columnar 
axis of the cloacal system consists of one large spiral fasciculus of spicula, each of which 
extends from the base or very near that part of the sponge, to near or quite to the apex 
of the column, the direction of the spiral being from right to left. 
There is a close approximate alliance to this form of the cloacal appendage of Hyalo- 
nema in the corresponding organs of the British genus Ciocalyjita^ Bowerbank, MS. 
IsoDiCTYA, Bowerbank. 
Spongia, Montagu. 
Halichondria, Fleming. 
Halichondria, Johnston. 
Skeleton without fibre ; composed of a symmetrical network of spicula ; the primary 
lines of the skeleton passing from the base or centre to the surface, and the 
secondary lines disposed at about right angles to the primary ones. Propagation 
by internal, membranaceous, aspiculous gemmules. 
This genus, in the structure and arrangement of its skeleton, is intermediate between 
