118 Mr. H. J. Carter on the Development 
some of the fibre has a stellate or rayed form, there is not 
another recorded instance in which there is the slightest 
resemblance of the horny fibre to the thousand and one known 
forms of spicules which exist among the sponges. And even 
here Fritz Miiller’s ‘ favourite”’ hypothesis (loc. cit. p. 351), 
viz. that in evolutionary development a horny form of the 
sponge-spicule precedes the siliceous and calcareous ones, 
is not borne out by the facts that in the first order, viz. the 
Carnosa (according to my classification), the first family, viz. 
the Halisarcida, possesses neither fibre nor spicules, that 
the second family, viz. the Gumminida, possesses spicules but 
no fibre, and that it is not until we reach the Ceratina and 
other orders that the jibre is developed. So with the deve- 
lopment of the sponge from the ovule, the spicules of the 
species are already seen in the embryo, while the fibre does not 
appear until the embryo has become fully developed into the 
young sponge (‘ Annals,’ 1874, vol. xiv. pls. xxi. and xxi. 
fig. 34, respectively). 
Again, if I am right as to the sequential way in which the 
fibre and the spicule are formed, the core or axis receives in the 
one as well as in the other its respective coverings at once, 
and not by transition; that is, the kerasine alone is deposited 
in the former and kerasine suspending silex in the latter. 
Thus Schmidt’s statement, in 1866, that the siliceous spicule, 
when deprived of its silex by fluoric acid, leaves a horny form 
(“‘ Hornnadel,” Spong. Adriatisch. Meeres, 2nd Suppl. p. 21), 
by no means confirms Fritz Miller’s hypothesis, as was in- 
tended, which, in an evolutionary point of view, as before 
shown, is not substantiated by either phylogenetic or ontoge- 
netic development. 
Moreover I have studied Darwinella aurea myself inde- 
pendently, as my naming a specimen Aplysina corneostellata, 
which came from the N.W. coast of Spain, will show, and 
find that to identify the stellate development of the fibre 
with the spicules (“‘ Nadeln”’) of a sponge requires a stretch 
of imagination which the anatomical facts, forms, and mea- 
surements that I have long since published (‘ Annals,’ 1872, 
vol. x. p. 101, pl. vu.) do not justify, any more than the 
phylogenetic and ontogenetic development to which I have 
just alluded. Hence I do not think that the term ‘ Horn- 
nadeln ” should be applied to this fibro-stellate structure. 
I can see no more analogy between the fibre and the spicule 
than that above mentioned. ‘They are as distinct from each 
other as the ligamentous structures and bones of the human 
subject, where, under normal conditions, the former never 
become the latter nor the latter the former. 
