THE ANATOMY OF AN AUSTRALIAN LAND PLANARIAN. 67 
action of the re-agents employed, especially when these penetrated slowly, and in 
such cases the lumen of the canal was found clothed by irregular heaps of granules, 
such as had been previously figured by Moseley. (6) Outside of the epithelium no 
firm canal wall was found, but the cells were placed immediately upon the surrounding 
connective tissue, or at most there were a few muscle fibres in the neighbourhood of 
the canal and its diverticula. 
The histological structure of the alimentary epithelium in Geoplana spenceri 
agrees fairly well with what is here described by von Kennel for the German land 
Planarians. The cells are usually more or less columnar in outline, with oval, 
granular nuclei and great numbers of highly refractive granuies, which are probably 
identical with the concretions mentioned by von Kennel and the granules figured 
by Moseley. Sometimes, however, owing possibly to scarcity of food, the large 
eranules are absent, and the protoplasm of the cells appears much more abundant, 
finely granular, and vacuolated. Figure 16 is drawn from a section cut with the 
freezing microtome from the anterior end of a young specimen killed with 
osmic acid and stained with borax carmine before cutting. From this figure 
it will be seen that the epithelial cells are not always arranged in a single layer, as 
described by von Kennel, though such is frequently the case. The cells here 
figured resemble those lining the lumen of the pharynx excepting in the presence 
of the abundant granules, which is doubtless due to the exercise of a digestive 
function not possessed by the latter. Digestion is obviously intracellular. 
A slight, but highly interesting modification of the digestive cells occurs in the 
main canal just before its anterior termination, as observed in a specimen killed with 
corrosive sublimate and cut by the ordinary paraffin method. The wall of the 
alimentary canal is here made up of a single layer of closely packed, very much 
elongated cells, each with an oval, granular nucleus in its basal portion. The base 
of the cell, containing the nucleus, is slightly expanded, and is followed by a very 
long and narrow neck, projecting into the lumen of the canal and terminating in a 
large, swollen head of irregular shape. The difference in the nature of the cell- 
contents in the different portions of one and the same cell is very striking. ‘The 
part containing’ the nucleus, and also the neck of the cell, are uniformly but finely 
granular, and stain moderately, the granules being placed close together. The 
irregular free termination of the cell, however, is in itself quite hyaline and 
transparent, and does not stain at all, but it contains a considerable number of large 
granules scattered irregularly through it, and these stain very deeply. The Ameba- 
like irregularity in the form of this portion of the cell leaves little doubt in my mind 
that during life it exhibited more or less active amceboid movements, feeding like an 
Ameba, and passing the digested food alone through the narrow neck to the deeper 
part of the cell, and thence to the tissues beneath. That only the digested food is 
