86 Records of the Indian Museum. [Vol. XIX, 



Internal anatomy. 



The oral sucker leads back into a short and wide pre-pharynx 

 (fig. I, pph.) with thin walls, and this is followed by a well-devel- 

 oped muscular phar^^nx {ph.). Liihe in his original description 

 states that this organ is rounded with a diameter of o*o75-oioo 

 mm. : in my examples it was only in the smaller specimens (vide 

 Table II) that the organ presented a rounded outline ; in all the 

 larger specimens the pharynx was oval, the long axis being in the 

 transverse diameter. The diameter ranges from o"o64 mm. in the 

 smallest example to 0*105 mm. in the largest. At first sight 

 it appears as if the pharynx did not increase in size proportionately 

 with the rest of the body, for in example 5, ^although the total 

 body-length is three times as great as in example i, the diameter 

 of the pharynx has only increased by 50 per cent. ; but, as I 

 have already pointed out, this increase in the body-length mainly 

 affects only the post-acetabular region and a comparison of the 

 other measurements shows that, so far as they are concerned, the 

 proportional increase in size is approxmiateh' also 50 per cent. 

 Behind the pharynx is a short wide oesophagus (oes.)^ the wall of 

 which is plentifully provided with muscles. The tube is lined by 

 a layer of cells having a finely granular protoplasm, and outside 

 this lies a double muscular coat ; the internal layer consists of 

 circular fibres surrounding the tube, and outside this is a layer of 

 oblique, strong muscle-fibres (fig. 2 exm.), which are attached to 

 the oesophageal wall and diverge outwards and forwards, blend- 

 ing with the supporting parenchymatous tissue of the body : 

 external to this again is a further layer composed of a number of 

 pyriform cells (oesg.), with oval or rounded nuclei. Monticelli 

 (1893, p. 30) has described this layer of cells in other trema- 

 todes as the salivary gland ; it is unfortunate that he should 

 have used this term, for Looss (1895, p. 140) has described true 

 *' salivary glands," the ducts of which pass forwards to open just 

 behind the mouth, in Pleurogenes claviger (Rud) and Heterolope 

 leptostoma (OIss.). In the former species the salivary gland 

 consists of 5 — 6 large granular rmcleated cells lying behind the 

 pharynx on either side of the oesophagus ; from each of these 

 cells a fine duct extends forwards, and they open in a row just 

 behind the mouth, the orifice of each duct being visible as a small 

 refractile spot. 



In Mesocoeliuni sociale (Liihe) true salivary glands (fig. 2 salg.) 

 also occur, situated behind and to the outer side of the pharynx 

 at the level of the bifurcation of the oesophagus. Each gland 

 consists of about ten pyriform cells, with round clear nuclei and 

 granular protoplasm : these glands are very difficult to see owing 

 to their being surrounded by follicles of the yolk-gland, but their 

 position is shown in fig. 2. From each cell a fine duct arises 

 {said.) ; these pass forwards in a bundle lateral to the phar^aix 

 and reach the side of the oral sucker ; they then sweep round its 

 dorso-lateral aspect and open in a transverse row on the anterior 

 lip of the mouth, the terminal portion of each duct appearing in 



