148 HALOMKNIA GRAVIDA. 



and lack any very definite arrangoiiu-iit further than that they encircle the 

 enormous papilhie, giving the animal as seen under low magnification, a mottled 

 appearance. 



The anterior pedal gland occupies the major portion of the space inckuled 

 between the gut (Plate 22, fig. 1), and body wall from the level of the brain to 

 the stomach-intestine. Its cells are comparatively small but the secretion is 

 abundant, enabling one to follow in many cases the slender ductule to its opening 

 into the anterior end (jf the pedal furrow. The walls surrounding this external 

 outlet are unfolded (Plate 22, fig. 1), highly ciliated and form a cavity of more 

 than usual size. From its posterior border two I'idges develop (Plate 22, fig. 2) 

 and extend along the pedal furrow to within a short distance of the cloaca, where 

 they disappear though the furrow, reduced in size, becomes continuous with the 

 cloacal cavity. 



In surface view it is jjossible to detect slight folds in the exposed cloacal 

 wall which in sections may be seen to become of much greater height within. 

 These, twenty-six to thirty in number, at first hang freely in the cloacal chamber 

 (Plate 22, fig. 11), but more anteriorly they become attached to the wall of the 

 rectum, antl yet farther forward some of the dorsal ones extend into the cavity 

 above the rectum dividing it into a corresponding number of small crypts (Plate 

 22, fig. 8). In these last named spaces, and between the folds for some distance 

 more posteriorly, upwards of twenty embryos have taken refuge and undergone 

 the first stages of their development protected by the parent. The epithelium 

 of the basal half of each io\d in contact with the embryo is low and seemingly 

 non-ciliated, while that of the distal half assumes the high colunmar, ciliated 

 appearance characteristic of such organs in several other species. 



As noted previously the cirrose section of the gut, or the atrium, opens 

 subterminally and has no direct connection with the remainder of the digestive 

 tract. Its cavity is largely obscured by the thick-walled, large ciliated ridges 

 which hold the usual position and define the cirrose area. The cirri are com- 

 paratively short and thick set and are usually united by their bases in groups of 

 two or four. Their cells are of the customary pigmented type and surround a 

 lumen of exceedingly small calibre. 



Immediately behind the opening into the atrium the cuticle surroumling 

 the body becomes continuous across the mid line for a short distance, and still 

 more posteriorly breaks through to form a second opening, probably the true 

 mouth. This aperture leads into an irregularly shaped cavity (the general 

 arrangement shown (Plate 5, fig. 3), whose walls, seemingly ciliated throughout. 



