120 STROPFIOMEXFA FARCIMEN. 



In several impditant particulars the digestive canal of the present species 

 resembles that of other members of Strophomenia. The atrial ridges are, as 

 usual, two in mimber and enclose the cirrose area; the more external is horse- 

 shoe-shaped and is composed of slender cohinmar, ciliated cells which contain 

 spindle-shaped nuclei and a very small amount of pigment. External to the 

 outer one is a low ridge of somewhat similar cells which, as in P. hmvaiiensis, 

 rests upon a rod-like mass of ganglion cells. The cirrose area is rather small in 

 extent (Plate 7, fig. 1), and the finger-like processes, arising separately from the 

 bounding wall, are composed of the usual pigmented cells, internally limiting 

 an exceedingly slender cavity penetrated basally at least by delicate strands of 

 connective tissue and probably nerve fibres. The opening from this sensory 

 atrium into the succeeding portion of the gut is bounded by a ring-like fold, 

 which is probably capable of protrusion to the exterior as it is supplied vvitli 

 numerous muscle fibres. Beyond this proboscis the pharynx pursues its way 

 for a distance almost as great as in Strophomenia scandens. In the early part 

 of its course its lumen is small, owing to the heavy folds developed in its walls 

 (Plate 17, fig. 11), but more posteriorly, and especially in the neighborhood of 

 the radula, it becomes a canal of greater size. As far posteriorly as the forward 

 end of the radula its walls are supplied with numerous glands, consisting of many 

 small, pyriform cells, united into bundles by means of connective-tissue fibres, 

 opening probably by separate intercellular crevices into the pharyngeal cavity. 

 In the neighborhood of the opening of the radula sac the canal, probably to be 

 considered as the oesophagus, again narrows, and its walls, composed of high 

 columnar cells, become developed into high ridges extending nearly to the 

 centre of the lumen. 



The radula is well developed and typically located, but the teeth composing 

 it are thin and delicate, since the sections display few traces of displacement 

 owing to the sectioning process. In cross sections it is very difficult to determine 

 the exact number of teeth, but there appear to be fifteen rows of from 24-28 

 in each row each having the form represented in (Plate 34, fig. 15). The base- 

 ment membrane is continuous across the mid line, but the bases of the teeth are 

 so fused that at first sight the radula appears to be of the distichous type. 



The dorsal intestinal coecum is of great length, as in Strophomenia scandens, 

 and is filled, as is the gut, by vast numbers of what appear to be partially digested 

 nematocysts. In a few places ova, probably rasped from the tissues of the host, 

 occur within the food mass. The cells lining the intestinal tract are highly 

 vacuolated and difficult to clearly define. The gut pouches likewise lack the 



