366 Mr. H. J. Carter on Spongilla. 
So long as these monociliated cells are only seen in the struc- 
ture of Spongilla their nature remains doubtful, as they may 
belong to something else ; but when they are found in distinct 
cells in the midst of this structure there can no longer be any 
room for such doubt. In their isolated state the spermatozoa 
have been seen and figured by many ; but no one has ever wit- 
nessed their entry into the ovum (which is the concluding 
point), except Prof. Hickel. The four cilia attached to the 
ovum of Leucandra aspera figured by Keller are, of course, 
only conjectural of this (see ‘ Annals,’ 1879, vol. iv. p. 383). 
Fain would I now with my present knowledge return to 
the examination of Spongilla in its living state; but the time 
and opportunity for this are past, while upwards of five-and- 
twenty years have elapsed since Lieberktihn and myself 
worked at the subject; and no one having again taken it up 
leads me to hope that ere long the coincidence of taste and a 
residence where Spongilla grows may be followed by resumed 
investigation ; for there is yet very much to be learnt of the his- 
tology and vital economy of the sponges generally, and none 
afford such facilities for this as those which grow in fresh water. 
My chief object now, however, is to call attention to the 
presence of a cell-structure in Spongilla, which is like that 
of the polygonal parenchyma of plants, and the presence of 
which could hardly be anticipated by those who have only 
studied the marine sponges, and know no other persistent 
structure beyond the spicules and the horny fibre, espe- 
cially one which if seen by itself would unhesitatingly be 
pronounced to be phytord. Nevertheless it is a fact, as I first 
showed in 1859, when I made the illustrated comparison be- 
tween the statoblast of Spongilla Cartert and the winter-ege 
of the Polyzoon Lophopus, to which I have already alluded 
(pl. vii. figs. 1-4). By reference to this communication it 
will be seen that there ds a tissue of this kind in Spongilla, 
and that it.surrounds the statoblast of S. Cartert in the form 
of a thick layer composed of hexagonal cells regularly ar- 
ranged in columns perpendicular to the following coat énwards 
of this spheroidal body. This I noticed again last year to be 
the case with the statoblast of Spongilla nitens (‘ Annals,’ 1881, 
vol. vii. p. 89, pl. v. fig. 3, d and 2); but although so large 
in these two species as to be visible with a “ doublet,” it can- 
not be seen in the statoblasts of other sponges with the same 
power, although it is more or less present ina great many, 
and gives them that white colour which often characterizes 
this reproductive organ. When too minute to be seen without 
a very high power, as in Spongilla alba, Parmula (Spongilla) 
Batesit, &e., it presents a granular appearance, for which 
