MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 163 



branches run along the dorsal sides of the hepatic ducts giving off a branch to each lobule. The 

 duct of the right lobes of the liver passes under the first loop of the intestine as this runs 

 forward around the coecum. The intestine passes backward under the median part of the liver, 

 nearly enclosing it in a loop. 



Valenciennes has figured an exceedingly interesting abnormality in his specimen. The anus 

 i- shown situated upon the body wall between the shell muscles. This is the only record of any 

 such misplacement of the anus. Valenciennes's specimen seems to be perfectly normal in every 

 other particular. 



We have no knowledge regarding the innervation of the portions of the alimentary system 

 back of the buccal mass. It has so far been impossible to trace any nerves to these organs. 



RENAL ORGANS. 



It has already been mentioned several times that the renal organs of Nautilus are situated in 

 the posterior region of the ventral portion of the mantle. Like the gills, they are four in 

 number, the renal glands being situated upon the branchial arteries. 



From the posterior side of each branchial artery, at about one-third the distance from its 

 origin to the base of the gill, hangs a large bunch of finger-like follicles. (Fig. 36, a. p. g. and 

 P- P- »•) These hang into the pericardial cavity. On account of their resemblance in many ways 

 to the pericardial glands of the Dibranchiata the four follicular appendages from the posterior 

 sides of the branchial arteries are also generally called pericardial glands. 



From the anterior side of each branchial artery, immediately opposite the follicular 

 appendage, hang two appendages subdivided by narrow fissures into small, polygonal lobes, 

 pressed closely together so that they appear to form a single hemispherical mass of about the 

 same size as the follicular appendage on the posterior side of the artery. (Fig. 37.) These have 

 been called the renal appendages. Each pair of renal appendages hangs into a chamber, the renal 

 sac, which is completely closed off from the ccelom, and has but a single opening to the exterior, 

 situated upon the inner surface of the mantle. (Fig. 36, r. s; Fig. 3, RA, RP.) 



The renal sacs are arranged in pairs; an inner (anterior) pair which lie side by side intdianly, 

 possessing a common dividing wall, and an outer (posterior) pair, which lie at either side of and 

 slightly posterior to the inner pair, nowhere touching each other. 



The dorsal or outer walls of the anterior sacs are formed by the integument of the mantle. 

 The ventral or inner wall is formed by the viscero-pericardial ligament (Fig. 36, p. v. 1.), which is 

 continued forward to unite with the integument of the mantle. A common, thin, vertical par- 

 tition separates the two sacs medianly. 



The posterior walls are formed by a narrow septum, extending between the viscero-per- 

 icardial ligament and the inner wall of the mantle. A section of either sac parallel to the 

 longitudinal axis of the body is triangular — the base of the triangle being posterior and formed 

 by the last-mentioned wall of the sac, while the apex is directed anteriorly and is formed by the 

 union of the edge of the viscero-pericardial ligament to the inner wall of the mantle fold. 



The longest diameter of the chambers is transverse to the long axis of the body. Passing 

 toward the sides the chambers gradually decrease in size; finally, near the outer ends, forming 

 a canal only, which leads to the external opening. 



To the outer sides of the lobular appendages the branchial vein, passing through the mantle 

 to the heart, pushes the walls of the sac inward from the posterior edge. (Text-tig. 9, BVA, Y.) 

 A short, blind pocket is formed upon the posterior side of the branchial vein. The narrow 

 portion of the renal sac anterior to the vein forms the canal leading to the exterior. This passes 

 the anterior side of the vein, then turns backward below the vein and opens outward just pos- 

 terior to it, through the outer of the two pores lying side by side upon the inner surface of the 

 mantle. (Fig. 3, RA.) 



The anterior branchial arteries pass outwardly from the vena cava in the posterior walls of 

 the anterior renal sacs. Each passes below the canal of the sac leading to the exterior, and on 

 in the mantle to the gill along the ligament-like base of the anterior gills. It thus lies immedi- 

 ately below the branchial vein. 

 Vol. 8— No. 5 5 



