170 THE ANNELIDES. <§> 157. 



only in the anterior segments of the body/"' With the genus Lumbricus, 

 the cardiac organs consist of five to nine pairs of moniliform, transverse 

 canals, situated above the stomach, and whose pulsations are very dis- 

 tinct.'^"' With all the Abranchiati yet examined, the blood is red. 



With the Capitibranchiati, there are often two dorsal vessels, one imme- 

 diately subQutaneous, the other lying, as usual, on the intestine.'"' This 

 duplicity of the dorsal vessel is observed particularly with those species 

 which have a coiled intestinal canal.''-' In this case, there is also a second 

 ventral vessel accompanying the coils of the intestine. All these longitudi- 

 nal vessels interanastomose very frequently, and send many transverse 

 branches to the intestine and the walls of the body, where they blend with the 

 capillary system. Not unfrequently, the dorso-intestinal vessel is dilated 

 at its anterior extremity, above the pharynx, into a large, pulsatory, heart- 

 like canal, which sometimes has two lateral arcuate, sinuses situated at the 

 commencement of the intestine.''"' The extremity of this vessel sends off, 

 right and left, many branches to the branchiae, which are situated in this 

 region. Leaving these organs, these vessels are distributed, some in front 

 to the tentacles, and to the other organs surrounding the mouth ; while 

 others pass below to unite with the ventral vessel. As the blood is thrown 

 from behind forwards in the dorsal vessel, and thence passes into the bran- 

 chiae, this vessel may be called a dorsal vein, and its dilatation a branchial 

 heart ; while the ventral vessel, which receives the returning blood from the 

 branchiae, would be an abdominal aorta. But there are other reasons for 

 this view. The dorso-intestinal vessel, from its intimate connection with the 

 liver, might well serve the function of a Ve?m portarum, while the close 

 union of the ventral vessel to the ventral cord, is undoubtedly for the purpose 

 that the latter, as a central nervous mass, may receive arterialized blood di- 

 rectly from the branchiae. With these animals (the Capitibranchiati), the 

 blood is red in some, and green in others."^' 



The Dorsibranchiati often have double dorsal and ventral vessels, two of 

 which belong to the intestinal canal, and two to the walls of the body.'^^' 

 With some, these longitudinal vessels are divided into two or three branch- 

 es.'^''' The principal dorsal vessel is sometimes dilated at its anterior ex- 

 tremity, above the pharyngeal tube, into a cardiac sinus, to which, at the 

 beginning of the intestine, there are added two lateral, arcuate dilatations. '^'^^ 



9 Ejichyfraeus, Chaetof^aster, and Nats. The constriction at its posterior part ; see Rathki, loc. 

 vascular system of Euaxcs and Lumbriculus is cit. p. 89, Taf. VI. fig. 5, f. {,'. 



very remarkable in tills respect. Instead of trans- H With Terebella, Amphitrite, and Serpula, 



verse anastomoses, there are, in each segment of the the blood is red ; with Sip/wnostomum, Chlorae- 



body, two vessels which pass off from the dorsal ma, and some species of Sabella and Serpula, it is 



trunk, and divide into many coecal branches ; see green. 



Treviranus, Beobaoht. aus d. Zoot. loc. cit. p. 60 ; 15 We are indebted to Milne Edwards for very 



and Grube, in Wiegmann^s Arch. 1841, I. p. 205, detailed accounts of the vascular systsm of the Dor- 



Taf. VII, fig. 1, 2, d. sibranchiati ; see Ann. d. Sc. Nat. loc. cit. PI. XII. 



10 See Duges, loc. cit. PI. VIII. fig. 1, and Mor- XIII.; see also, for that of Arenicola, Stannius, 

 ren, loc. cit. p. 162, Tab. XX.-XXIII., XXI.- in Muller's Arch. 1810, p. 357. 



XXIV. fig. 1. 16 With Eunice sanguinea, there is a double 



11 Milne Edwards has made very beautiful re- dorso-intestinal vessel {Milne Edwards, loc. cit. 

 searches upjn the vascular system of the Capiti- PI. XII. lig. 2, 3 ' ) ; and a doulile ventral one 

 branchiati ; see Ann. d. Sc. Nat. X. 1838, p. 193, with Nephtys Homber^i. With Arenicola, there 

 PI. X. XI. are three ventral vessels accompanying the ventral 



12 Amphitrite and Siphonostomum ; see Rath- cord {Mailer, in Burdach\i Phys. loc. cit. p. 147). 

 Ac. Danzig. Schrift. loc. cit. p. 76, 88, Taf. V. fig. 4,5. and with Amphinome, Grube has found three 



13 With Terebella, there is a vascular heart and dorsal ones beside, all widely separated from each 

 two lateral sinuses; see Milnt Edwards, loc. cit. PI. other. 



X. XI. fig. I. With Siphonostomum, there is a li Eunice ; see Milne Edwards, loc. cit. PI. 

 similar cardiac dilatation upon the pharynx, and it XII. fig. 2. The vascular system here resembles 

 is divided into two chambers by a well-marked that of Terebella. 



