Points ill the Ilistolagy of Coelenterates. 259 



regard llie cells ns nervous. It is impossible to specify a 

 definite form lor tlic cells; indeed, we arc really unable to 

 ppoak of " sojmrate " cells at all, for not only do very broad 

 and sliort 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- 

 S])ondingly 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. These aggregates of cells (in which 

 limits are absolutely indistinguishable) lie 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, 1 Avill 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 ganglion-cells of the higher animals. The finer the 

 processes become — and there are very delicate ones which 

 remind us of those of the Medusas — the more difEcult becomes 

 their distinction from processes of the ordinary e|)it!ielio- 

 rauscle 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 tlie 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 notliing 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 bs 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 ForshaJea there is a 

 thickening of the ectoderm containing structures which at 

 first attracted my attention very forcibly. Subsequently, on 



