THE ANATOMY OF AN AUSTRALIAN LAND PLANARIAN. 59 
At the point marked c in figures 8 and 9 the transition between the ciliated and 
glandular epithelium is very abrupt indeed, as shown in figure 7. This was observed 
in two distinct series of sections. In other places it is not so easy to make out the 
boundary line between the two kinds of cells, but it appears to be generally better 
marked along the dorsal margin of the glandular epithelium than along the ventral. 
In some parts also the glandular cells are not nearly so distinctly flask-shaped as in 
the portion figured, being more irregularly massive and often also of smaller size. 
This is especially the case towards the ventral border of the glandular zone, and 
perhaps we have here a more or less gradual transition between the two kinds of 
epithelium. 
I have spoken of the peculiarly modified epidermic cells as glandular without 
being able to offer any absolute proof that they are so; still I think there can be 
little doubt of the correctness of the view I have taken. They probably secrete a 
fluid which fills the peripharyngeal cavity, and may be of service as a lubricant in the 
protrusion and retraction of the pharynx through the very narrow opening of the 
cavity in which it lies. The coagulated remains of such a fluid are visible in my 
preparations. These cells are not, however, the only structures from which such a 
fluid may have been derived, for in the angle where the pharynx joins the wall of the 
cavity the ordinary glandular tissue (to be described later on) appears strongly 
developed beneath the epidermis. This tissue by itself, however, would scarcely be 
sufficient to secrete all the fluid necessary to fill the cavity. 
Perhaps stronger arguments in favour of the glandular nature of the modified 
epidermic cells are to be found in their peculiar structure, and in the difficulty of 
assigning to them any other function. They appear to be merely modifications of the 
ordinary columnar cells of the epidermis, and to be the only true gland cells existing 
in that layer. They probably discharge their contents by rupture of the cell-wall at 
its outer extremity. 
B.—The Basement Membrane.—This is distinctly visible in some preparations as 
a very thin, structureless layer, immediately underlying the epidermic cells, just as 
described by Moseley (6) ; but very often it cannot be made out as a distinct layer. 
C.—The Muscular System.—With regard to the muscular system of Geoflana 
spenceri, the first feature which strikes the observer is its close correspondence in 
arrangement with what Moseley (6) has described in Bipalinm and Rhynchodemus, 
and later (1) in Geoplana traversii. So close is this agreement that were it not for the 
fact that I wish to give as complete an account as possible of the minute anatomy of 
Geoplana, which may be of use especially to Australian students, and also to 
enunciate certain views, which I believe to be new, regarding the homologies of the 
muscular systems in the land and fresh-water Tricladians, it would scarcely be 
