STUDIES ON THE TURBELLARIA. 455 
one of Béhmig’s “ Porenkanilchen ”—which perforate the 
basement-membrane and the cells. The appearances repre- 
sented, however, correspond neither to the Triclad Dendro- 
ccelum nor to the Polyclad Planocera. 
Digestive system.—The pharynx belongs to the type of 
von Graff’s “ pharynx rosulatus,” which is characteristic of 
the Mesostomida and Proboscida. It is of rounded 
shape, its oral opening situated near the anterior end of its 
ventral wall, and its cesophageal near the posterior end of its 
dorsal wall. A thin, external, circular layer of muscular 
fibres lies outside the longitudinal layer. The latter consists 
of a single layer of broad flat fibres, whose edges are in close 
apposition. In the dorsal and ventral, but not the lateral, 
walls the radial muscles are arranged in regular rows. Be- 
tween them are the gland cells, the secretion of these is very 
fluid, and, in the living specimens, is to be observed to run 
freely backwards and forwards in the spaces between the 
radial muscles. The internal circular layer of muscular fibres 
is much the thickest. The internal hning membrane has lost 
its epithelial character, and presents no trace of division into 
cells, though a nucleus occurs here and there at wide intervals. 
A number of unicellular glands lie around the junction of the 
pharynx with the intestine. 
Retractor and protractor muscles pass from the pharynx 
through the parenchyma to the muscular layers of the body 
wall. One strong bundle passes straight forwards in the 
middle line from the anterior wall of the pharynx to the 
anterior extremity of the body, causing the brain to be slightly 
indented on its lower surface as it passesit. Itis accompanied 
by red granular matter which renders the whole structure 
somewhat conspicuous in the living animal. 
The intestine has an irregular space representing the lumen 
bounded by a masss of cells, which does not assume the 
character of an epithelium, and is not bounded externally by 
any muscular or fibrous layer. ‘The enclosed cavity, though 
irregular in shape, must be fairly constant in position, since 
the dorso-ventral muscular fibres which traverse its wall in 
