BLOOD-VASCKLAK SYSTEM OK THK TILK-KISH. 



101 



arises about 2 cm. from the ventral end of the artery and runs toward the median 

 lino, where it may join the corresponding artery of the opposite side to form a single 

 vessel — the dorsal median hypobranchial artery {52). As a rule, however, it does 

 not roach the median line, but curves caudad dorsal to the fourth division of the 

 musculus obliquus ventralis, and terminates, like the dorsal median hypobranchial, 

 in the musculus constrictor pharyngis and inferior pharyngeal teeth. The branches 

 of the fifth commissural artery are the dorsal coronary artery (49), which is given 



Fig. 12.— Ventral ends of the efferent branchial vessels and their branches in the tile-fish. Ventral 



aspect, x'2. 



off from either the right or left side, and two pairs of nutrient branches which go to 

 the fourth ( JV) and to the rudimentary fif th (50) branchial arch. In one case the 

 vessel which supplied the rudimentary fifth arch was joined by a branch (51, fig. 12) 

 from the left fourth efferent branchial artery; also, in one individual the fifth com- 

 missural artery was wanting, its place being taken by the sixth, which was present 

 only on one side and arose from the fourth efferent branchial vessel. 



Summing up the arrangement of these vessels in the tile-fish, it will be seen 

 that the species possesses dorsal as well as ventral coronary arteries, a dorsal and 



