HISTOLOGY OF THE LAND-PLAN ARIANS OF CEYLON. 
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Digestive System. — As is usually the case in Planarians, the digestive canal is single 
anteriorly and double posteriorly in both Bipcdium and Bhynchodemus ; and a similar 
condition exists in Geoplana (Max Schultze, loc. cit. 4, p. 35). From the opening of the 
pharynx into the digestive tract forwards there is a single straight and broad digestive 
tube, which gives off diverticula or caeca on each side, and breaks up into ramifications 
in the head. At the opening of the pharynx this single tube becomes split into two 
branches, which diverge widely to . pass one on each side of the sheath which contains 
the pharynx and which forms their inner wall ; they approach one another somewhat- 
more closely as they pass on each side of the sheath containing the generative organs, 
which lies immediately behind that of the pharynx and is continuous with it. Pos- 
teriorly to this point a stout septum runs down the median line of the body to the very 
tip of the tail, and separates the two tubes from one another, forming their inner wall 
on each side. This septum is continuous with the sheath of the generative organs 
superiorly ; and, indeed, these organs and the pharynx might justly be said to be contained 
in spaces hollowed out in the septum itself. These points are displayed in Plate XII. 
fig. 2. 
There is no perforation in the septum, and thus the two posterior canals have no 
communication with one another behind the point at which they branch off from the 
single anterior tube. From the outer surface of the lateral walls of the digestive canals 
arise stout transverse septa, which pass outwards to join the lateral region of the 
muscular body-mass. These septa are parallel both in Bhynchodemus and Bijgalium , 
excepting at the immediate anterior and posterior extremities of the animal. The 
intervals between them are diverticula or cseca, which communicate with the intestinal 
tube by means of apertures in its wall. These diverticula are present in the posterior 
part of the body only, on the outer side of the two intestinal tubes, as is also the case in 
Geoplana (Darwin, loc. cit. p. 243). The parallelism, approximation, and enormous 
number of digestive diverticula form the characteristic point of resemblance between 
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