Miss J. Sollas on Haddonella Topsenti. 559 
sponges and discusses Janthella at some length. He speaks 
of the cells in the fibres as “ pigmented cells,” and at one 
stage of his argument comes to this conclusion: “ the horny 
laminze were not only deposited on the grey granuliferous 
axis, but the horny material itself was formed by the pig- 
mented cells.”” Carter, however, considers he is bound to 
reject this conclusion, because such a mode of formation of 
spongin is not known in other horny sponges, and he thinks 
that his choice of a spongin-former lies between the axis of 
the fibre and the surrounding “ sarcode.”” He chooses the 
latter alternative. He has not seen, nor apparently sought, 
the fibre-tips. 
Polejaeff (2) examined the species I. flabelliformis. He 
states that the cells in the fibres occur between the laminze 
of spongin, as Carter had described it, the laminz being con- 
centric cylinders about the axis of the fibre, and he shows 
this well in his fig. 5, pl. 2. He speaks of the cells as in all 
probability spongoblasts, and he seems to have been the first 
to take this view. He failed to find any part of the fibre 
without cells or without spongin cortex, and consequently 
there was a difficulty in accounting for the origin of the pith. 
Polejaeff’s work, ‘On the Structure and Classification of 
Horny Sponges,’ 1886, being written in Russian, was not 
accessible tome. In the‘ Challenger’ report Polejaeff speaks 
of the inclusion of spongoblasts in the horny substance of the 
fibres as a peculiarity of which the systematic importance is 
‘rather ambiguous.”” He then remarks that ‘if we should 
in time find Janthellide, 7. e., horny sponges whose skeletal 
fibres are charged with true cells, of thoroughly different 
organization, we should be obliged to elevate the character in 
question to the rank of that of a subfamily, or even family ” 
2) 
Q Von Lendenfeld (3) describes three species, J. flabelliformis, 
I. basta, and I. concenitrica. He criticizes Polejaett’s account 
and especially his fig. 5, pl. 2, which he says is very incorrect, 
and adds :—‘“ The cavities ” (2. e., the cell-containing cavities 
in the cortex of the fibre) ‘‘ are embedded in spongin which is 
clearly stratified in such a manner that the layers are deter- 
mined by the cavities and strictly parallel to their surfaces” 
(the italics are his). The fig. 1, pl. 49, of the Monograph 
illustrates this statement clearly and shows a structure such 
as one might perhaps have expected on @ prior? grounds. 
The structure 1 have observed in the skeletal fibres of Had- 
donella agrees well with Polejaeff’s figures, and with those 
published earlier by Flemming and Carter (6 and 7). : 
Von Lendenfeld describes the stratified spongin as passing 
