PLANARIANS FROM MAURITIUS AND RODRIGUES 141 
constantly being secreted in greater or less quantities, and gives 
rise to a thin layer between the ventral surface of the body and 
the substratum. In this case rhythmical wavy motions of the 
muscles stand, of course, in intimate relation to the movements. 
Digestive System.—The mouth-opening, which lies 
nearly in the centre of the body, leads, as usual, into the wide 
peripharyngeal cavity with the pharynx horizontally disposed. 
The cavity is lined with a single layer of epithelial cells made 
up of pear-shaped cells of a glandular nature, as has been stated 
by Dendy in G.spenceri. The epithelium rests upon a fine 
basement membrane, beneath which are two layers of circular 
and longitudinal muscular fibres. Situated in the parenchyma 
around the cavity are unicellular glands which open into the 
cavity 
The pharynx is a short, tubular body of a cylindrical shape, 
which arises from the dorso-anterior wall of the peripharyngeal 
cavity, with its free end posteriorly directed. The outermost 
layer of the wall is represented by a very thin, richly ciliated 
epithelium, immediately beneath which come, as usual, two 
thin layers of external longitudinal and internal circular 
muscles. The circular layer is followed, after an interval in 
which glandular and nervous tissues exist, by a very thick layer 
of longitudinal muscular fibres. Just external to this layer 
comes a layer of circular fibres, immediately surrounding the 
lumen of the pharynx, which is lined by a single layer of non- 
ciliated cells. Besides the muscles mentioned above, there are 
found a number of radial fibres, running from the inner circular 
layer towards the outside. 
The lumen of the pharynx leads anteriorly into the intestinal 
canal, which is of the triclad type. The anterior trunk extends 
to a point above the brain and usually gives off on each side 
numerous lateral branches, which are sometimes bifurcated and 
sometimes trifurcated. The posterior trunks proceed back- 
wards nearly to the hind end of the body, one on each side of 
the middle line, and are provided with numerous outwardly 
directed, subdivided branches. The wall of the intestine is 
a single epithelium made up of high cylindrical cells, which are 
