PACHYMENIA ABYSSORUM. 75 



traces of food were found in the tract and accordingly we are without any knowl- 

 edge of the animal's feeding habits. 



The walls of the cloaca! chamber are provided with a number of slender 

 outpouchings and to these are attached multitudes of gland cells grouped into 

 lobules of different sizes. Each cell is pyriform and contains a somewhat granu- 

 lar slightly vacuolated secretion that makes its way by a delicate ductule through 

 an intercellular opening into a diverticulum of the cloacal wall. The general 

 arrangement of these structures is shown in Plate 39, fig. 2. 



The pericardial cavity is comparatively spacious and the contained heart, 

 consisting of two divisions, is moderately muscular. The aorta in the present 

 specimen is of small size but in its relations to the gonad and the anterior end 

 of the body it is typical. Owing probably to the size of the foot the ventral 

 sinus is large and connects in the usual fashion with the head sinuses and here 

 and there throughout the body with the visceral sinus. In the posterior part 

 of the body it divides, passes dorsally on each side of the intestine and after 

 passing posteriorly for a short distance breaks up into a small number of lacunae 

 which connect with the gills. From these organs the blood passes through rather 

 ill-defined channels in the somatic musculature to the posterior end of the heart. 



Five or six pairs of relatively large folds appear in the cloacal wall running 

 more or less parallel to the outer opening near which they are situated (Plate 39, 

 fig. 2). Here and there these develop numerous minor wrinkles (Plate 40, fig. 7) 

 which pass from one main fold to another or extend some distance over the 

 cloacal wall. As usual they all contain blood sinuses but otherwise are not 

 especially modified. 



The brain, imbedded in the numerous glands attached to the forward wall 

 of the pharynx, is an unusually elongated structure and without distinct signs 

 of being bilobed. From its anterior face the usual nerves, heavy in appearance, 

 are distributed to the body wall and the ganglionic masses about the bases of 

 the cirri. The lateral, pedal, and labio-buccal connectives arise from the ex- 

 treme lateral boundaries of the brain and follow the usual course. A very slight 

 enlargement marks the point of union of the lateral ganglion with the corre- 

 sponding connective, while one of twice the diameter occurs in the case of the 

 pedal cords. The last named structures are united at fairly definite intervals 

 by clearlj' defined commissures and about the same number of connectives 

 attach to the lateral ganglia. A nerve from the anterior pedal enlargement 

 passes to the wall of the outlet of the anterior pedal gland, and two branches 

 originate from a corresponding point on the lateral ganglia and applied to the 



