THE ANATOMY OF AN AUSTRALIAN LAND PLANARIAN. 55 
also very unsatisfactory for this purpose, although they show plainly enough the cilia 
on the ventral surface, which are difficult to make out in sections similarly prepared 
from ordinary spirit-preserved material. I have obtained by far the most satisfactory 
results in this respect from variously prepared transverse sections of a small 
specimen which I killed with osmic acid. Some of these sections were cut with 
the freezing microtome and stained, some with borax carmine and others with 
Kleinenberg’s haematoxylin, after being cut. The difficulty in using the freezing 
microtome is to get the sections thin enough. Those stained with Kleinenberg’s 
haematoxylin proved to be the best, and they demonstrated at once the very 
important fact of the existence of a perfectly distinct row of nuclei in the deeper 
portion of the epidermic layer, both on the dorsal and ventral surfaces. These nuclei 
had hitherto entirely escaped my notice, nor had they been previously observed by 
Moseley. Von Kennel (8), however, has noticed their occurrence in the German 
land Planarians investigated by him, and Jijima (7) describes and figures them in the 
fresh-water Tricladians. 
In order to obtain thinner sections I resorted to the ordinary paraffin method, 
after staining with borax carmine, and figures 5 and 6 are based upon one of these 
preparations. Owing doubtless to the heat employed in melting the paraffin, the 
cellular constituents of the epidermis appear somewhat shrivelled up in these 
preparations, but this is not altogether a disadvantage as it is of some assistance in 
determining the boundaries between adjacent cells. 
I shall now describe the structure of the epidermis in Geoplana spenceri, and it 
must be borne in mind that in this, as in other cases, my description and figures are 
the result of the examination of a very large number of sections prepared in a variety 
of ways. 
The epidermis, as is well known in other forms, is not of the same thickness all 
over the body, being very much thicker on the lateral and dorsal than on the ventral 
surface. I have observed cilia on the ventral surface only. Moseley (6) concludes 
that in Bipalium and Rhynchodemus cilia are present all over the body, although he 
did not succeed in making them out on the dorsal surface. He further adds “‘ Max 
Schultze, though he did not see cilia in Geoplana, yet concludes that it must be covered 
all over with them from the experiments of Fr. Miiller, who covered the body of one 
of these Planarians with arrowroot, and observed a motion of the particles which 
served to show the presence of cilia. Darwin came to the same result from the 
observation of the motion of air-globules in the slime of Geoplana. Mecznikow found 
the skin of Geodesmus bilineatus covered with cilia.” 
In a later paper (1) the same author states that in a transverse section of a fresh 
animal (Geoplana flava), examined in saliva, cilia were present over the entire dorsal 
surface, where, however, they are very short and difficult to see, whereas they are very 
