THE CEPHALOPODA. 



449 



chamber can be fully distended without the air passing into 

 the other. 



Fig. 12?. — Sepia officinalis. — c. systemic heart : ao. anterior aorta ; ao', posterior aorta ; 

 1, vena cava; 2, afferent branchial vessels: re. renal organs; 2. appendages of 

 these vessels ; 3, 4, lar^e posterior veins bringing blood to the afferent branchial 

 vessels ; 5, 6. 7, efferent branchial vessels, branchial veins,-and branchio-cardiac 

 or auricular trunks. (After Hunter.) 



In Nautilus pompilius there are, as Valenciennes discov- 

 ered, three pairs of openings which lead from the branchial 

 sac into chambers contained in the interior of the body. Of 

 these chambers there are five : the anterior and posterior 

 pairs are situated on each side of the rectum, and each has 

 its own opening ; the fifth, a very much larger chamber, has 

 two openings, one on each side. It is coextensive with that 

 part of the mantle which lies behind the insertion of the shell- 

 muscles and the horny band which connects them. It is 

 separated from the paired chambers by their inner walls, and 

 these walls are traversed by the afferent branchial veins. 

 Appendages of these veins project on the one hand into the 

 paired chambers, and on the other into the single chamber. 

 The latter appendages are elongated papilla?, while the for- 

 mer are lamellar. Earthy concretions, composed mainly of 

 phosphate of lime, but which yield no trace of uric acid, are 

 usually found in the paired sacs. 1 



1 Owen, " Memoir on the Pearly Nautilus." Van der Hoeven, " Beitrasr 

 znr Anatomie vom Nautilus pompilius" (" Arehiv far Xaturgeschiehte, 1 ' 

 1857). Huxley. "On some Points in the Anatomy of Nautilus pompiUus n 

 (" Proceedings of the Limvean Society," 1858). See also Keferstem, Bronn's 

 44 Klassen u. Ordnungen," Bd. iii. (18G2-'66), pp. 1390, 1319. 



