1920.] R. B. Seymour Sewell : M esocoelium sociale. 



87 



optical section, exactly as Looss describes, as a round refractile 

 spot. It is extremel}^ interesting to note that these gland-cells and 

 ducts agree exactly as regards their appearance and distribution 

 with the ''stylet-gland" cells of the Polyadenous group of the 

 Xiphidiocercariae [vide Cort, 1914, p. 53 and figs. 68 and 69), 

 and I have no doubt that the two structures are identical. 



About midway between the pharynx and the anterior margin 

 of the acetabulum the oesopljagus divides into two wide intestinal 

 caeca {fig. i i), the lumen of which is lined with finely granular 



Sal. 



Fig. 2. — Anterior region of Mesocoeliitm sociale (Liilie). 

 exm., external muscle-fibres of oesophagus; genp., genital pore ; m., mouth 

 met., metraterm ; oesg., oesophageal gland cells ; pli., pharynx ; ppli., prepharynx 

 said., ducts of salivary glands ; salg., salivary gland; 5.';'., seminal vesicle; vd. 

 vas deferens ; ve., vas efferens. 



cells. Each caecum passes backwards and outwards around the 

 acetabulum and is then continued back along the sides of the bod}^ 

 to a point about one-third of the total bodjMength from the. 

 posterior end. Liihe in his original description states that the}^ 

 extend back three-quarters of the body -length, but here again 

 there seems to be some difference in different individuals, according 

 to the degree of development that has been attained. A reference 

 to Table II shows that in smaller specimens the caeca extend pro- 

 portionately further back in the body than they do in the larger 



