764 



ZOOLOGY 



SECT. 



which is not drawn out into a tube. There is no communication 

 between the cavities of the different sacs, and thus no median 

 chamber as in Sepia, and there is also no communication with the 

 pericardium. The cavities are found to contain phosphate of 

 lime. Into each projects, from the corresponding afferent 

 branchial vein, a compact rounded group of venous appendages 

 (ren. app.), consisting of two symmetrical portions. Internal to 

 these, each afferent vein has connected with it a second group of 

 glandular appendages, which are cylindrical or club-like in form ; 

 they project, not into the nephridial sac, but into the peri- 

 cardial compartment of the coelome. They have been compared 

 with the appendages of the branchial heart of Sepia, but differ in 

 their relations to the renal appendages. 



FIG. 692. Nautilus pompilius, renal sacs, with ctenidia and other related parts, as seen 

 from the posterior aspect ; the boundaries of the four renal sacs represented by dotted 

 lines, a. I. aff. left oral afferent vessel ; cten. right ctenidia ; I. neph. ap. left oral renal 

 aperture ; I. neph. s. left renal sac ; I. post. neph. ap. left aboral renal aperture ; /. post, 

 neph. s. left aboral renal sac ; l.v.ap, left viscero-pericardial aperture ; p. 1. aff. left aboral 

 afferent vessel ; p. r. aff. right aboral afferent vessel ; r. ant. aff. right oral afferent vessel ; 

 r. ant. aur. right oral auricle ; ren. app. renal appendages ; r. neph. ap. right renal aperture ; 

 r. neph. s. right renal sac ; r. post. aur. right aboral auricle ; r. post. neph. s. right aboral renal 

 sac; r. v. ap. right viscero-pericardial aperture ; ven. c. vena cava; vent, ventricle ; vise, 

 per. s. viscero-pericardial sac. 



Nervous System. Nautilus differs strikingly from Sepia, and 

 somewhat resembles Chiton (p. 698, Fig. 614) in the form assumed 

 by the central parts of the nervous system v(Fig. 690, cer. g.), 

 distinct ganglia being absent. A very thick nerve-collar, 

 the posterior portion of which is double, surrounds the oesophagus. 

 The anterior part of the collar (Fig. 690, cer. g.) represents the 

 cerebral ganglia, the oral portion of the posterior part the pedal 

 (ped. g.), the aboral portion the pleuro-visceral (pi. g.) ; while the 

 lateral parts, not distinctly marked off from the rest, represent the 

 cerebro-pedal and cerebro-pleural connectives. From the cerebral 

 ganglia pass nerves to the buccal mass, to the olfactory organs 

 (olf. n.) and the statocysts, and a pair of very thick optic nerves 



