130 
MR. H. N. MOSELEY ON THE ANATOMY AND 
Mhynchodemus and Bipalium, and one in which they differ widely from all the flattened 
Planarians whose anatomy has as yet been carefully described ; and the septa seem to 
foreshadow the transverse septa connecting the intestine to the body-wall in Annelids. 
In the anterior and posterior extremity of the bodies of Mhyncliodemus and Bipalium 
the diverticula take an oblique direction, and are given off fanwise from the termination 
of the digestive tube. In Mhynchodemus the arrangement at the anterior and posterior 
extremity is much the same and the diverticula are simple ; but in the head of Bipa- 
lium these secondary tubes are ramified to a considerable extent without retaining any 
parallelism, as may be seen in Plate XII. fig. 1, and at this part of the body resemble 
very much in their ramifications those of the digestive tract of the flat aquatic species. 
The diverticula communicate with the main digestive tubes by means of oval per- 
forations in the walls of those tubes ; and these oval apertures are often, but not always, 
disposed in pairs. In Mhyncliodemus the diverticula are simple, but in Bipalium they 
are partially split up into two or four compartments by means of secondary and tertiary 
septa, which extend from their outer extremities through a portion of their length. The 
septa, when cut transversely in a longitudinal section of the animal’s body, are found, 
both in Mhynchodemus and Bipalium , to consist of two muscular walls, between which is 
a quantity of the peculiar glandular matter already described as existing in the other parts 
of the body. The muscular fibres of the septa are, as has been also stated, finer than 
those of the general body-mass ; hut occasional stout fibres, taking a more or less vertical 
direction, are to be seen in transverse sections of the septa. In the neighbourhood of 
the pharynx, the wall of the main anterior digestive canal is strengthened by special 
longitudinal muscular fibres. The pharynx, or muscular prehensile apparatus forming 
the entrance to the digestive tract, and by means of which the food is taken into the 
body, is contained in a receptacle or sheath formed of the same material as the median 
septum of the posterior portion of the digestive tract and continuous with it. This 
sheath has an extremely elongated oval form in Bipalium , and a shorter oval one in 
Mhynchodemus ; and it .communicates with the exterior in each case by means of a 
circular aperture, which has been termed the mouth. In Geoplana the mouth is 
described by Mr. Darwin as being a transverse slit, not circular, as is here the case. 
The pharynx, which, when the animal is in search of food, is protruded through the 
mouth, lies ordinarily entirely out of sight within its sheath, to the dorsal surface or 
wall of which it is attached by strong muscular roots. Claparede was mistaken in 
supposing that a folded pharynx was characteristic of Land-Planarians. Though the 
pharynx of Bipalium is thus constructed, that of Geodesmus hilineatus (Mecznikow, 
loc. cit.) and of Mhynchodemus is cask-shaped or cylindrical. The pharynx of Bipalium 
has been described and figured by Claparede. It is (Plate XII. fig. 3) of an elongated 
form, and consists of a pair of closely apposed tumid lips, thrown by contraction into a 
series of transverse folds. Between the lips, somewhat anteriorly to the centre of the 
organ, is the aperture which leads, by means of a short canal, to the opening (O, Plate 
XII. fig. 3) into the digestive tract, which opening lies just in front of the anterior 
