RESPIRATORY CIRCULATION IN FISHES. 271 



cular system of the Loligo, detached from the 

 surrounding parts ; the course of the blood being 



indicated by arrows, c is one of the three 

 trunks constituting the venae cavae, proceeding 

 from above, dividing into two branches as it de- 

 scends, and terminating, conjointly with the two 

 venous trunks (d), which are coming from below, 

 into the lateral or branchial hearts (e, e), already 

 mentioned. Thence the blood is conveyed by the 

 branchial arteries, (f, f), on each side, to the gills 

 (g), and returned, by the branchial veins, (i), to 

 the large central, or systemic heart (l), which 

 again distributes it, by means of the systemic ar- 

 teries, to every part of the body. The cuttle-fish 

 tribe is the only one thus furnished with three 

 distinct hearts for carrying on a double circula- 

 tion : none of these hearts are furnished with 

 auricles. 



