Points in the Histolagy of Colenterates. 259 
regard the cells as nervous. It is impossible to specify a 
definite form for the cells; indeed, we are really unable to 
speak of “ separate” cells at all, for not only do very broad 
and short processes connect the masses of protoplasm, which 
figure as cells, in the longitudinal direction of the stem, but 
it is usually the case that instead of one nucleus and a corre- 
spondingly smaller size the latter is actually very consider- 
able, and a number of nuclei (I counted as many as five) are 
present in the interior. ‘hese aggregates of cells (in which 
limits are absolutely indistinguishable) le with their elon- 
gated direction crosswise to the stem; they are in continuity 
with the rest by means of the short thick connecting portions, 
and from them there also radiate the nerve-fibres, which are 
often of extraordinary thickness, ramify like processes of 
ganglion-cells, run transversely to the stem beneath the 
epithelium, and probably also penetrate down to the muscles 
beneath. As regards the structure of these fibres, as well as 
of the cells and cell-masses, I will merely mention that there 
is a fluid in their interior which exudes in drops when they 
are crushed and is perhaps comparable to the hyaloplasm 
of the ganghion-cells of the higher animals. The finer the 
processes become—and there are very delicate ones which 
remind us of those of the Medusee—the more difficult becomes 
their distinction from processes of the ordinary epithelio- 
muscle cells, and they are besides frequently just as irregular 
as the latter (on this point see the complete paper). In 
general the amount of fluid too appears to be no certain 
criterion; on the contrary, it only implies that the cells and 
cell-offshoots in question are thick and rounded, while this is 
not the case for the majority of epithelial cells, since they 
appear as if flattened out perpendicularly to their longitudinal 
elongation in their deeper parts, and above all in the broad 
basal process; the protoplasm here has often only the thick- 
ness of an even tolerably delicate membrane. In spite of all 
these odd features it nevertheless appears to me that we must 
regard the large elements of the dorsal side as nervous, for 
there is nothing else that could otherwise be considered as 
such; and although the epithelio-muscle cells are here 
and there provided with cilia (usually two together), we 
cannot on that account term them tactile cells with Korotneff, 
with whom a cilium is sufficient to cause a cell to be regarded 
as sensitive. I shall endeavour to give further support to my 
interpretation in my complete work. 
At the basal end of the polypes of Forskalea there is a 
thickening of the ectoderm containing structures which at 
first attracted my attention very forcibly. Subsequently, on 
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