276 MR J. T. CUNNINGHAM ON 



pared transverse sections in continuous series from specimens preserved with 

 picro-sulphuric acid, and stained with borax-carmine. The specimens chosen 

 for this purpose were of the medium size, carrying about 16 suckers. The 

 sections are all very similar to one another, differing chiefly in the relation 

 which they bear to the series of suckers. In one taken from the middle of the 

 series, the intestine is seen in the centre, elliptical in outline, the long axis of 

 the ellipse being dorso-ventral. The epithelium of the intestine is thick, and 

 composed of large nucleated cells, which form sometimes more than one layer, 

 and are not quite regular in arrangement. Both in the living animal and the 

 prepared section it can be seen that the cells of the intestinal epithelium are 

 rapidly proliferating ; the free ends of the cells project into the lumen in various 

 degrees, and a number of detached cells are seen lying free in the interior. 

 In the living animal these cells float about under the influence of the move- 

 ments of the body, and are occasionally expelled from the mouth. Some of 

 them contain minute round granules. 



On each side of the intestine is the section of one of the main lateral 

 excretory canals, in which there is no distinct epithelium to be seen. There 

 are nuclei in the walls, and the cavity may be lined by an epithelium of ex- 

 tremely thin cells, to which these nuclei belong. The walls of the canal are 

 extremely thin. 



The parenchyma of the body, or mesenchyma, appears in the sections as a 

 fine reticulum with deeply stained nuclei at the nodes. The actual structure of 

 the mesenchyma in Trematocles has been much disputed,"" some observers 

 maintaining that the intercellular spaces are globular and the cells stellate ; 

 others, vice versa, that the cells are globular, and the intercellular spaces reticu- 

 late. In the living Stichocotyle the mesenchyma is seen to be crowded with 

 minute bright refringent granules, which seem to be contained in intercellular 

 spaces, as they move through considerable distances in parts of the animal 

 Avhich are in active contraction. They are shown in fig. 3. 



The muscular layers of the body wall are imperfectly differentiated ; they 

 arc represented by a zone of closely crowded nuclei at the periphery of the 

 mesenchyma, and, external to this, a zone of small dots, which are probably 

 the sections of longitudinal fibrils. The account of the muscular layers of the 

 integument in the young of Amphilina, given by SALENSKY,t agrees pretty 

 closely with the state of things in my sections, except that he mentions nuclei 

 in the external of the two layers, and in the zone of dots I have described 

 there are no nuclei. 



The sucker is composed chiefly of elongated cells, whose long axis is per- 

 pendicular to the epidermis. These are simple muscular cells which dilate the 



* Vide Fraipont, loe. cit., p. 428. 

 f Zeit. f. tvis. Zool, Bd. xxiv., 1874. 



