174 



THE ANNELIDES. 



^160. 



It is remarkable that the branchiae are perhaps entirely wanting, with 

 the Aphroditae/'^' while they are often highly developed, partly in a 

 pectinate and partly in a fasciculate manner, with the Euniceae, Amphino- 

 mae, and Arenicoiae.® 



with Glycera, Nere'in, Lycastis, Nephtys, and 

 others ; but with Cirratulus, they are very long. 

 With Phyllodoce, a id Atciopa^ there are flat- 

 tened lobules. 'BvAsYiihLumbrinereis, Aglaura, 

 and some other aUied genera, these are wholly 

 wanting ; see Milne Edwards, Classif. loc. cit. 

 The question here arises if the Dorsibranchiati 

 which have atrophied branchiae, have not there- 

 fore internal respiratory organs. It is at least 

 probable that the two pahs of remarkable net- 

 works surrounding the pharynx of Nereis and 

 which have given rise to various interpretations 

 (see Rathki, De Bopyro et Nereide, p. 48, Tab. II. 

 lig. 5, bb, fig. 8, f, g, h, and Tab. III. fig. 14 ; 

 also Milne Edwards, Ann. d. Sc. Nat. X. 1838, 

 p. 210, PI. XII. fig. 1,0, p) are properly internal 

 branchiae. They receive the blood from the dorsal 

 vessel through two lateral vessels, and it is returned 

 to the median ventral vessel by two others which 

 are also lateral. Moreover, according to Rathki 

 (loc. cit. p. 40), there is, between every two feet 

 upon both sides of the segments of the body, a small 

 orifice opening into the cavity of the body and 

 tlirough which water for respiration can pass. 



7 Different observers have equally different 

 opinions upon the branchiae of these animals. For 

 my own part, I have found no trace of these 

 organs, either internal or external with Aphrodite 

 aculeata, and hystrix. I suppose, therefore, that 

 water enters the cavity of the body by orifices 

 which are very small and difficult to be seen, and 

 comes in contact with the entire vascular system. 



Milne Edwards (Rögne anim. illustr. Ann6- 

 lides, PI. XVIII. fig. 2", c) has figured rudiment- 

 ary branchial lobules with Aphrodite aculatea, 

 which are crenulated and concealed between the 

 scales, and are, perhaps, invisible, when the animal 

 is in a fresh state. Moreover, Sharpey (Cyclop. 

 Anat. and Phys. I. p. 618), having observed with 

 the same species a very active ciliary motion espe- 

 cially upon the external surface of the uitestine 

 and its coeca, it is very probable that here, aa with 



the Astero'idae, the respiration occurs by water 

 entering the cavity of the body and bathing the 

 intestine. 



S With Onuphis, and Eunice, the branchiae 

 are pectinate or semi-pinnate ; see Milne Ed- 

 wards, Classific. loc. cit. With Diopatra, and 

 Chloeia, each branchia consists of a single ramified 

 fasciculus ; but with the Amphinomae, and Areni- 

 colae, there are several fascicuU ; see Milne Ed- 

 wards, loc. cit. and his plates annexed to R^gne 

 anim. de Cuvier, Annelides ; also Stannius, Isis, 

 1831, Taf. VI. With Eunice, the blood of the 

 median dorsal vessel passes first into the inferior 

 lateral vessels which have the form of cardiac 

 sinuses, and by the pulsations of which it passes 

 into the branchial vessels, whence it returns into 

 the other two dorsal vessels by the superior lat- 

 eral ones ; see Milne Edwards, Ann. d. Sc. Nat. 

 X. 1838, p. 207, PI. XII. fig. 2. 



With Amphinome, there is at the base of each 

 branchial fasciculus, in the cavity of the body, a 

 Plexus branchialis, closely resembling the won- 

 derful net-works of Nereis, and from which the 

 blood passes into two lateral vessels which here 

 exist ; see Catal. of the Physiol. Ser. &c. 11. PI. 

 XIV. fig. 10, or Rymer Jones, Outlines, &c., p. 

 218, fig. 93. 



With Arenicola piscatoriim, only the thirteen 

 middle segments of the body have branchial fas- 

 ciculi. These communicate with the ventral and 

 dorsal vessels by simple lateral vessels. 



As there exist here at the extremity of the body 

 between the two dorsal and ventral vessels, two 

 cardiac sinuses, it is probable that these force the 

 blood from before backward into the ventral vessel, 

 and thence by the lateral vessels into the branchiae ; 

 so that these inferior lateral vessels would be 

 called arteries, and the superior lateral vessels 

 which return the blood to the dorsal vessel, veins ; 

 see Milne Edwards, Ann. d. Sc. Nat. loc. cit. p. 

 215, PI. XIII.* 



* [ § 160, note 8.] The respiratory organs of the 

 Annelides have been much studied by (^uatrefa- 

 ges (Ann. d. Sc. Nat. XIV. 1850, p. 290), and the 

 following is his resum^ : 



" 1. The respiration is at first general and en- 

 tirely cutaneous (^Lumbrinereis, Lysidice, He- 

 sione, &c). 



"2. It is stijl cutaneous, but is confined or concen- 

 trated upon particular rings of the body (Ckae- 

 topterus). 



" 3. It is localized upon certain points of each 

 ring, without the structure of these points being 

 fcensibly modified (Nereis). 



" 4. The first degree of the specialization of the 

 respiratory organ ajjijears under the form of a sim- 

 ple cul-do-sac, or an ampulla into which the blood 

 flows {Glycera). 



"6. The branchiae become gr.adually character- 



ized by the formation of a canal which communicates 

 with the more or less spacious lacunae. 



" 6. These true branchiae may be distributed all 

 along the body (Eunice sanguinea). 



" 7. They may be concentrated upon a certain 

 nimiber of rings situated near the middle of the body 

 (Eunice Bellii, Arenicola, Hermella, Polydora). 



" 8. They may be concentrated towards the ante- 

 rior extremity of the animal, and occupy only a few 

 rings (Terebella, Pectenaria). 



" 9. Finally, they may be located wholly at the 

 extremity of the body, and form only a double tuft 

 (Sabella, Serpula). 



" 10. In considering sometimes the entire body, 

 sometunes each ring separately, a real distinction 

 between the venous and the arterial system may 

 nearly always be made out."- Ed. 



