of the Fibre in the Spongida. 115 
under the microscope—the horny laminzs may be seen to be 
almost wholly composed of them in a moreor less flattened state, 
corresponding with the thinness of the lamina in which they 
are imbedded (figs. 12, 6, and 14, 6) ; while in one specimen, 
viz. that from Dr. Bowerbank’s collection before mentioned, 
where the cells and their coloured contents have so disappeared 
as to leave nothing but their empty cavities, the horny lamin 
present nothing but a reticulated structure of kerasine 
(tinged with carmine from the escape and diffusion of the 
colouring-matter), and the axis consists of the colourless 
or grey granuliferous substance already described. Again, if 
by taking a very early development of this fibre, in which 
it is very thin, we lessen the number of the horny lamine 
one after another down to the axial granuliferous substance, 
the last horny layer (fig. 13, 6) will be found to possess com- 
paratively very few pigment-cells, where it rests immediately 
on the granular core, which, on the other hand, contains none 
(fig. 13, a). 
So that, in fact, we are reduced to the conclusion that the 
horny lamin were not only deposited on the grey granulife- 
rous axis, but the horny material itself was formed by the 
pigmental cells, which would become substantiated if the horn 
lamine generally (that is, in all other sponges) presented this 
cellular structure in an equally evident degree; but they do 
not; on the contrary, the higher the magnitying-power that is 
put upon them in most other sponges but Janthella, the more 
homogeneous their composition appears to be. Hven in the 
Luffarida and Aplysinida, where the pigment-cells are as 
purple and as defined as in Lanthella itself, there is not a ves- 
tige of them to be seen in the horny lamine. 
Thus we are compelled, so far as the purple pigmental cells 
are concerned, to attribute the formation of the horny lamin 
either to the grey granuliferous substance of the axis on the 
one side, or to the granuliferous transparent sarcode of the 
general parenchyma on the other—either to the addition of 
the lamine internally from the axis, or externally by some 
other agency. 
Studying the early development of the axial substance, 
which, being so like the granuliferous transparent portion of 
the sarcode or parenchyma, can hardly be distinguished from 
it, in the absence of the horny lamine, it is not uncommon to 
find in the Aplysinida separate globular horn-cells more or less 
elongated and branched, arrested on their way to the forma- 
tion of fibre, and thus rendered abnormal products, in all of 
which the grey granuliferous material occupies the axis 
(fig. 1,9); so that I have long since termed such bodies 
