184 REPORT — 1851. 



agent of the circulation is seen in the large oesophageal dorsal trunk, which 

 commences at the confluence of the intestinal longitudinal vessels. The 

 ventral-most of these latter, on rising to the dorsal aspect of the canal and 

 meeting in the common dorsal oesophageal, produce, as in T. nebulosa, the 

 appearance of the vascular ring encircling the oesophagus. The infra- 

 neural or ventral trunk, bearing a current from the branchiae and tentacles 

 to the intestine and integument, constitutes the apparatus for the systemic 

 distribution of the blood, the dorsal oesophageal being the true branchial 

 heart. The alimentary canal, posteriorly to the ring-vessel, is embraced in 

 a framework of four longitudinal trunks, severally communicating through 

 the medium of glandular capillary plexuses. The peritoneal fluid in this 

 species is less voluminous than in the former. The peritoneal space is a 

 continuous chamber, and the parietes are vascular. The tentacles, orga- 

 nized nearly as in the former species, are smaller and fewer in number. 



The resemblance is remarkable betv/een the circulating system of the 

 Euniciadce and Terebellce. At an early period M. Delle Chiaje recognised 

 and described the leading features of the blood-system of Eunice gigantea, 

 under the name of Diopalre*. M. de Blainville has also given some account 

 of the circulation of this wormf. To Milne-Edwards belongs the honour of 

 having first fully and minutely investigated the anatomy of the circulatory- 

 system in this and other Annelida. In accuracy his description is not to be 

 surpassed. It is only in one particular that the author's account, which has 

 been drawn with repeated care from his own dissections, will be found to 

 differ from the statement of Milne-EdwardsJ. 



As a great degree of mobility is conferred upon the cephalic extremity of 

 the body in Eunice, and as the protrusile oesophagus is considerably less 

 vascular than the intestine, the great dorsal vessel occurs here as in the Te- 

 rebellce under the character of an wwbranching tube, reaching from the in- 



* Memoire sulla storia e uotomia degli Animali senza vertebre del regno di Napoli, t. ii. 

 p. 396. 



t Art. Vers du Dictionnaire des Sciences Naturelles, t. Iviii. p. 405. 



X Compare the diagram given by the French naturalist, of the circulating system oi Eunice 

 (pi. 12, fig. 2, Annales des Sciences Natm-elles, ser. 2, Octobre 1831) with the author's de- 

 scription as given in the text with reference to this Annelid, a worm which probably 

 attains less gigantic proportions in this country than on the southern parts of the coast of 

 France, and the reader will perceive that the lateral branches going, at each segment, into 

 the branchise, undergo no heart-\\k.e dilatation as represented in the illustration of Milne- 

 Edwards. In relation to these branches the description of this profound anatomist runs as 

 follows : — " Enfin par son extremite anteriem'e, le vaisseau dorsal envoie divers branches a la 

 tSte et d'autres rameaux qui se portent en dehors corame chez les Terebelles, mais qui, au 

 lieu de se rendre aux branchies, remontent en arrit-re et vont se distrihuer au pharynx ou 

 leurs divisions s'anastomosent avec celle du vaisseau ventral. Ce dernier tronc suit le meme 

 trajet que chez les Terebelles et donne egalement naissance, dans chaque anneau du corps, a 

 une paire de branches laterales. Mfiis la conformation de ces branches est differente ainsi 

 que leur usages. Aussitot apres sa naissance, chacune d'elles se renfle beauconp et se re- 

 courbe brusquement sur elle-meme, de fa9on a ressembler, lorsqu'on I'examine superficielle- 

 ment, a une vesicule o\iilaire, disposition qui a probablement induit en erreur M. Delle 

 Chiaje, quand il a aunonce I'existence d'ampoules ou pouches arrondies, situees sur le trajet 

 des branches laterales du vaisseau dorsal de I'Eunice gigantesque. Ces vaisseaus transversaux 

 se. portent ensuite en dehors, foumissent une branche ascendante au tube digestif, gagnent 

 la base des pieds, y donne naissance a plusieurs petites branches anastomiques dont la re- 

 union constitiie un lacis vasculaire, et a des ramuscules destines aux muscles et aux tegumens 

 voisins ; enfin penetrent dans les filamens branchiaux coiTespondans et s'y terminent. Le 

 sang qui a subi I'iufluence de I'oxygene, a travers la surface de ces appendices dermoides, 

 est refu dans d'autres canaux transversaux qui se dirigent vers le tube digestif en suivant les 

 cloisons interannulaires, et debouchent dans le vaisseau situe de chaque cote de la ligne 

 mediane sur la face dorsale de cet organe." In the references to the diagram Milne-Edwards 

 describes these lateral branches which supply the branchies, as " bulbes contractiles de ces 

 branches ' laterales' remplissant les fonctions de coeurs pulmonaires." — Op. cit. 



