338 A. E. Yerrill — JSforth American Cephalopods. 



the posterior aorta divides into three large arteries : one of these (o) 

 is situated in the median plane, and crossing the branchial cavity in a 

 curved line along the edge of the thin median membrane, supplies the 

 ventral and lateral portions of the mantle, sending branches both for- 

 ward and backward ; tlie other two main branches (o' o") diverge as 

 they go backward and supply the caudal fins and adjacent parts of 

 the mantle. The anterior aorta (wo) arises from the right anterior 

 corner of the heart, and goes forward to the head, on the right side of 

 the median line, T>y the side of the oesophagus, giving oii from its sides 

 various small l)ranches. Near its origin it is somewhat bulbous. 



The first branch, the gastric artery, arising not far from its origin, 

 sends a branch to the renal organs, and running backward over the 

 dorsal side of the heart, ramifies over both lobes of the stomach. 

 During its passage through the substance of the liver, and along 

 the groove on its dorsal side, the aorta gives ofiT several branches 

 which supply that organ with blood, while one artery, of consider- 

 able size, emerges from the posterio-dorsal side of the liver and 

 supplies the muscles of the neck ; others go out from the anterior 

 part of the liver, laterally and ventrally, to various parts of the head. 

 Ten large branches go to the arms, one running through the center 

 of each to the tip, sending off numerous lateral branches to the suckers 

 and other parts. Other branches supply the various organs of the 

 head. A small artery (fig. 2, go) arises from the anterior side of the 

 heart, and turning backward, supplies the spermary (^). The large 

 effei'ent vessels [hranchio-cardiac) from the gills [bo] enter the 

 anterio-lateral corners of the heart, their dilated basal portions serv- 

 ing as auricles. 



The branchial auricles (a?<), situated just behind the bases of the 

 gills, are nearly globular, with a small, rounded, whitish elevation 

 on the free posterior end ; dorsal ly they receive the blood from the 

 saccular divisions of the anterior and posterior vena^-cavaj [vc, vc') 

 and from the veins (y, ve') coming from the lateral portions of the 

 mantle, behind the gills ; and they give off the large afferent vessels 

 (bv) which go to and run along the dorsal side of the gills. 



The anterior vena-cava (vc) receives the venous blood from a large 

 cephalic venous sinus, which surrounds the pharynx, at the bases of 

 the arms,* and is connected with another large sinus situated at the 



* The greater part of the venous system can be easily injected by inserting a canula 

 into this sinus, through the fold of the buccal membranes between the bases of the 

 arms and the jaws, or between the outer and inner buccal membranes. It can also be 

 easily injected through the vona-cava in the lower side of the head. 



