XIII] SEPIA 317 



stomach and genital organ. These arteries have regularly formed 

 branches from which the blood enters definite veins. This formation 

 of well-defined channels for the blood is characteristic of the Cephalo- 

 poda. Of these veins the most important are : (1) the anterior 

 vena cava ; this is a channel in the mid-ventral line in front of the 

 kidneys, which forks and sends a branchial vein over each kidney to 

 the base of each gill ; (2) the abdominal veins ; these are a pair of 

 large channels which come from the mantle, especially the upper 

 part of it, and join the forks of the vena cava just before they enter 

 the gills ; (3) the genital vein ; this is a trunk draining the genital 

 organ, it runs along the posterior wall of the dorsal pouch of the 

 kidney and joins the right fork of the vena cava ; (4) a vein from the 

 ink-sac joining the same fork, and (5) on each side a smaller vein from 

 the mantle joining the main venous system at the branchial hearts 

 (Fig. 145). Where these veins come in contact with the kidney 

 wall the special excretory tissue mentioned above is developed. 



A peculiar feature in the circulatory system is the presence of a 

 pair of muscular swellings of the forks of the vena cava just before 

 they enter the gills. These are the branchial hearts, the 

 function of which is to drive the blood into the gills, whereas the 

 auricles drain it out of them. Each branchial heart projects on the 

 one side into the kidney and on the other side into the reno- 

 pericardial canal, and the epithelium of the latter where it covers 

 the heart is greatly thickened so as to form a cushion, the function 

 of which is excretory. This, like Keber's organ in the river-mussel, 

 is a remnant of the primitive excretory function which probably all 

 the cells of the coelom once possessed. 



The alimentary canal of Sepia is constructed on very much the 

 same plan as that of the snail. The mouth is situated in the centre 

 of the arms and surrounded with a frilled lip (Fig. 143). There is a 

 large buccal mass containing the radula and there are a pair of 

 powerful jaws shaped like a parrot's beak, movable on one another 

 of which the ventral is the larger. There are two salivary glands 

 and a long narrow oesophagus but no crop. The oesophagus widens 

 behind into the stomach, which receives, as is usual in Mollusca, the 

 ducts of the liver. With the stomach is connected a side pouch 

 spirally coiled. The liver is enormous, occupying all the anterior 

 portion of the visceral hump ; the ducts traverse the dorsal ex- 

 tension of the kidneys, and are in this position covered externally 

 with excretory tissue, which by the older naturalists was termed 

 "pancreatic" caeca (12, Fig. 146) from a mistaken comparison with 

 the human pancreas. The intestine is slightly bent on itself and 



