1869.] DR. J. 8. BOWERBANK ON SILICEO-FIBROUS SPONGES. 345 
fig. 5. These strongly marked points of resemblance in form and 
identity in relative situation and office between the auxiliary spicula, 
in addition to those of the skeleton, irresistibly lead us to the con- 
clusion that these sponges, however different in their forms, are 
structurally members of the same family. Strongly marked dif- 
ferences in form are apt to lead our judgments astray when super- 
ficial observations only are made of the specimens before us; but 
when we see such extraordinary variations of form occurring in the 
same species under different circumstances and amounts of develop- 
ment as those we observe in sponges with the habits of which we 
are perfectly familiar, as, for instance, in our protean species Hali- 
chondria panicea, we should be prepared to admit, as in truth we 
ultimately must do, the same latitude of variation among the nearly 
allied species and individuals of the same species of the siliceo-fibrous 
sponges. 
In all the numerous specimens of Aleyoncellum with which I am 
acquainted, the skeleton is composed of rigid inosculating siliceous 
fibre, as I have stated in my paper on Aleyoncellum speciosum, 
Proc. Zool. Soc. 1867, p. 351, in my description of the generic 
character in p. 353, in the following terms :—‘ Skeleton siliceo- 
fibrous ; primary lines radiating from the base in parallel, straight, 
or slightly spiral lines ; secondary lines at right angles to the pri- 
mary ones.” I will not reiterate here the full details of the struc- 
ture of these beautiful sponges that I have given in my paper as 
quoted above ; and such a repetition is the more unnecessary as 
they have been imported so abundantly of late as to place specimens 
for microscopical examination within the reach of almost every one 
interested in the subject. The sponges have also been figured in 
Trans. Zool. Soc. vol. iii., and in Trans. Linn. Soc. London, xxii. 
pl. 21, and also in the Ann. & Mag. Nat. Hist. for Feb. 1868, pl. iv. ; 
but in none of these plates is there any delineation of the skeleton- 
structure with a high microscopical power, and it is this want that 
I purpose at the present time to supply, that we may be enabled to 
arrive at a sound conclusion as regards its true skeleton-structure, 
and also as to such of its specific characters as have not hitherto 
been figured or described. 
Dr. Gray, in his “ Notes on the Arrangement of Sponges,” Proc. 
Zool. Soc. 1867, p. 492, has, at p. 504, described the Luplectellade 
(Aleyoncellum, Quoy et Gaimard) as having a “skeleton composed 
of longitudinal, transverse, and oblique bundles of spicules inter- 
secting each other and forming a network ;’’ and Prof. Wyville 
Thomson, in his paper on the “ Vitreous’? Sponges, Ann. & Mag. 
Nat. Hist. for Feb. 1868, p. 114, at p. 126, in his description of 
his proposed new genus “ Habrodictyon,’’ has adopted the error into 
which Dr. Gray has fallen by describing the skeleton as consisting 
“of a perfectly irregular network of siliceous needles loosely and 
irregularly arranged in sheaves crossing one another at low angles, 
and connected by a small quantity of soft mucilaginous sarcode.”’ 
These descriptions of the skeleton are, in both cases, completely 
erroneous, as can be readily demonstrated by boiling portions of the 
