48 Dr. D. Bersrendal on the Land-Planarice. 



■■to 



of structure in different parts. In some places we see the septal 

 {Balkenhildung) formation which is so much referred to ; in 

 others, the longitudinally running nerve-fibrils, cut across, 

 are very distinct. Between these longitudinal trunks there 

 are transverse commissures, which are very thin and often 

 branched, which is probably the reason why Moseley and von 

 Kennel did not see them. In older specimens, preserved in 

 alcohol, of Bipalium diana^ from the Zoological Museum in 

 Berlin, I have also found these commissures. Near the head 

 such commissures are particularly numerous. Further, strong 

 arched nerves are emitted outwards, and these form a plexus 

 under the skin. This plexus cannot be found everywhere ; 

 it is particularly well developed in the head and the fore part 

 of the body. Such peripheral branches often start from the 

 same spots as the transverse commissures, and at some of 

 these points of ramification the dotted substance and the 

 ganglion- cells become so numerous that one might almost 

 describe it as a ganglion-formation *. No thickening of the 

 longitudinal trunks was, however, observed. The ganglion- 

 cells are large, have very large nuclei which stain rather 

 faintly, and show two or three processes. The longitudinal 

 nerves decrease very much in size in the caudal extremity ; 

 they curve towards one another and unite. In the cephalic 

 portion is situated the flat and greatly extended brain, the 

 formation of which by the union and thickening of two longi- 

 tudinal trunks is to be recognized particularly distinctly in 

 the hinder part of the brain. In the lateral portions of the 

 brain we see great masses of dotted substance in transverse 

 sections. Numerous ganglion-cells also occur in the brain, 

 but their arrangement in the different parts cannot be described 

 without figures. 



Moseley has already stated that there are on the anterior 

 margin of the head some papillse, between which there occur 

 little pits furnished with cilia. These papilla?, which are 

 situated in a groove, are square in transverse section in B. 

 Tcewense, and show an epithelium of rather small cells. 

 The anterior surface of the papillae is not beset with mov- 

 able cilia ; the lateral surfaces bound the passages leading 

 to the pits and exhibit very strong cilia. The tissue of 

 the papillse consists in great part of muscular fibres, 

 which give the papilla great mobility. It is remarkable 

 that we see in the papillae no large nerve-trunks, nor is 

 there any structure of the epithelium which would seem to 

 indicate that they are sense-organs. The epithelial cells 



* lijima states that he found f^anglia in the freshwater Planarise, but 

 that they possess but few ganglion-cells. 



