806 
DE. J. S. BOWEEBANK ON THE ANATOSIT 
base, and tapering to invisible points at their free extremities ; they have no perceptible 
order of succession in their motions, nor are they synchronous, but strike the water by 
constantly and rapidly extending and inflecting themselves.” The author describes the 
attachment and spreading out into a thin disk of the ovum or gemmule, and the cessa- 
tion of action and gradual disappearance of the cilia ; and he further observes, “ although 
all ^dsible cilia have ceased to move, we still perceive a clear space round the ovum, and 
a halo of accumulated sediment at a little distance from the margin.” This observation 
is important, as tending to prove the existence of ciliary action, although the organs 
themselves were too minute to he detected. 
Dujardix, in his work on the Infusoria, in plate 3, fig. 19 5, represents what are 
apparently the detached cilia and their basal cells, and which were probably from 
Grantia compressa. 
If portions of a living sponge of this species be torn into small pieces, and placed in 
a cell in sea-water under a power of about 400 linear, groups of the detached cilia and 
their basal cells will be readily seen at the margins of the specimen ; they are usually 
thus clustered together, and have a tremulous and indistinct motion. If a small speci- 
men of the sponge be slit open and placed in a cell with fresh sea-water, with the inner 
surface of the sponge towards the eye so as to command a distinct view of the oscula, 
the cilia will be seen in the area of that organ in rapid motion, and the extraneous mole- 
cules attached to them exhibit the extent and nature of their oscillations very distinctly 
(Plate XXXIII. fig. 2). If the sponge he carefully torn asunder in a line at right 
angles to its long axis, and the torn surface be placed in a cell with a little fresh sea- 
water, we occasionally obtain a favourable longitudinal section of some of the large 
cells of the sponge, and we then see the cilia in situ and in motion (Plate XXXIII. 
fig. 1). 
The whole length of the cell, from the inner edge of the diaphragm to its origin near 
the outer surface of the sponge, is covered with tessellated nucleated cells, which have 
each a long attenuated and very slender cilium at its outer end. They are oval in form, 
and have a distinct nucleus. When in vigorous condition their motions are rapid and can- 
not readily be followed ; but in some in which the action was languid, the upper portion 
of the cilium was thrown gently backward towards the surface of the sponge, and then 
lashed briskly forward towards the osculum, and this action was steadily and regularly 
repeated. Their motions are not synchronous — each evidently acts independently of the 
others (Plate XXXIII. fig. 3, a & 5). 
The numbers, situation, and peculiarities of their actions fully account for the con- 
tinuous and powerful stream that issues from the great cloacal aperture of this and other 
similarly constructed sponges. The natui’al rate of the motions of these organs must 
not he estimated from the sections last described, but the estimate must be made from 
the appearances manifested at the oscular orifices at the inner surface of the sponge. 
A more detailed account of these investigations is published in the Transactions of the 
Microscopical Society of London, vol. iii. p. 137. Figs. 1, 2, 3, & 4, plate 7, represent 
