66 THE ANATOMY OF AN AUSTRALIAN LAND PLANARIAN. 
make out, they are quite irregularly arranged. They are compressed from before 
backwards, perhaps owing to the state of contraction caused by preservation, so that 
in a vertical longitudinal section of the entire animal they appear elongatedly oval 
in outline (Fig. 10. al. c.) 
In Geoplana traversti Moseley (1) describes and figures a remarkably regular 
arrangement of the openings of the lateral diverticula into the main canals. He says: 
“The arrangement of the openings of the diverticula into the main canals is shown 
in Pl. XX. Fig. 6. The mouths of the diverticula appear as vertically directed, 
irregularly oval slits which are arranged in a line on the outer walls of the main 
canals and are of two sizes, smaller ones alternating with larger. A narrow 
longitudinally directed groove or depression connects the middle of the mouths 
of the diverticula with one another.” According to von Kennel, Mecznikow 
also (whose original paper I have not seen) appears to have figured a regular 
arrangement of the diverticula in Geoflana. Von Kennel, however (Joc. cit.), denies 
their regularity, and observes, ‘‘ wie er es angestellt hat, solche Bilder zu eérhaltes, 
ist mir rathselhaft.” i 
Moseley (6) records the interesting fact that no diverticula are present on the 
inner side of the two posterior main branches in Bipaliwm and Rhynchodemus, but in 
Geoplana traversi he states (1) that they occur in the position named, as also is the 
case in Geoplana spencert. 
At the extreme anterior end of the animal the alimentary canal diminishes in 
size, and finally terminates in a small chamber above the nerve ganglion, as shown 
in figure 10. 
Histological Structure of the main Branches of the Alimentary Canal and their 
Dwerticula—Before describing the histology of the digestive epithelium in Geoplana 
spencert, it will be well to notice the-very concise observations of von Kennel (8) 
upon the subject. Von Kennel found everywhere a simple, high, cylindrical 
epithelium, the cells of which were placed very close together, and usually resting, 
not perpendicularly, but obliquely, on the surrounding tissue. Between the ordinary 
homogeneous and pale-coloured cells were found more or less numerous isolated, 
spherical cells, which appeared highly granular or reticulated, and which the author 
regards as unicellular glands. All the cells had oval nuclei in their basal portions, 
and in many larger or smaller brownish concretions oceurred at the central end of 
the cell, but these were not found in the so-called unicellular glands. In the adult 
animals the nuclei were so numerous and the cells so small that they were difficult 
to distinguish, and therefore not figured, but the author convinced himself that the 
epithelium always remained one cell thick, and he nowhere observed cilia. It was 
found that very often the alimentary epithelium was completely destroyed by the 
