THE CEPHALOPODA. 



449 



chamber can be fully distended without the air passing into 

 the other. 



Fig. 1-27.— Se2na officinalis.— c. syBtemic\\enrt ; ao. anterior aorta ; ao\ posterior aorta ; 

 1, vena cava ; 2, afferent branchial vessels ; re, renal ori,'ai;8 ; z, appendages of 

 these vessels; 3,4, lar<,'e posterior veins bringinir bloori to the afferent branchial 

 vessels ; 5, 6, 7, efferent branchial vessels, branchial veius,and brancbio-cardiac 

 or auricular trunks. (After Hunter.) 



In JVaictilus 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 connr^cts 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 papillae, 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.* 



> Owen, " Memoir on the Pearly Nautilu.**." Van der Hoeven, " Bcitrae 

 zur Anatomic vom Navtilvft pompilivs^^ (" Archiv fiir Naturoreschichte," 

 1857). Huxlev, "On some Points in the Anatomy of Nmitilus pompilius'''' 

 (" Proceeding's of the Linnfran Societv," 1858). See also Keferstcin, Bronn's 

 "Klassen u. Ordnungcn," Bd. iii. (18'62-'66), pp. 1390, 1319. 



