PHENOMENA IN SPONGES. 191 
magnifying power, even these granules cannot be perceived. 
Within the thicker trabeculz are placed the ciliated organs, 
which, like the trabeculz themselves, are also situated imme- 
diately beneath the external membrane, and in contact 
with it. 
In other cases the trabeculz have a totally different aspect, 
becoming moniliform or beaded, the constituent cells of 
which they are composed being distinctly defined. More- 
over, several rows of cells of this kind may be seen in 
contact, and the cells in such close contiguity that the 
whole appears like an epithelium detached from its sub- 
stratum. At the same time the cells may be globular or 
depressed, and may assume a stellate or polyhedral shape. In 
other cases, again, they are separated by a transparent 
substance, so that the whole filament appears even on the 
surface, globular or irregular masses being seen only in the 
interior, and which are also surrounded by a transparent 
substance. In these granular masses may frequently be 
observed nuclei, with nucleoli, which, in any case, belong to 
the cell-contents, whilst the transparent substance may be 
referred both to this as well as to the membrane. 
All the above-described conditions of the parenchyma may 
be witnessed in succession in one and the same specimen of 
Spongilla, and this even within so short a time that they must 
be regarded as motile phenomena. The observation may be 
very readily made under a low power in a suitable specimen, 
placed in a watch-glass filled with water. In this way the 
author observed the smooth, homogeneous septa become thick 
trabeculz, which presented a cellular structure and assumed 
the moniliform appearance. He also noticed how two fila- 
ments in contact with the external membrane, and each 
consisting of a single series of cells, and separated from each 
other by more than the diameter of a cell, became so con- 
joined as to constitute an apparently homogeneous septum. 
Within the space of half an hour this process extended 
over a great part of the sponge; whilst, again, in other 
places smooth fibres became moniliform. At the same time 
cavities, having a diameter equal to the length of a spicule, 
closed up, new ones making their appearance at other. points, 
and visibly enlarging whilst the observation was going on. 
Sometimes two cavities, separated from each other by a deli- 
cate septum, coalesced into a single one, by the enlargement 
of one of them, whilst the filaments became slenderer 
and slenderer, and ultimately united with the walls of the 
other cavity, which was all the while diminishing in size. 
In another instance the inhalent orifices of the outer mem- 
