Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    177/482 (page 173)
    arranged loops.® With Lumbricus, these aquiferous canals are sur- rounded by a very distinct vascular net-work, which has a botryoidal aspect from its numerous pedunculated, vesicular dilatations which are filled with blood.® § 160. With most of the Capitibranchiati, and Dorsibranchiati, the respiratory organs consist of external branchiae, which are very apparent, although having variations in their development. They always consist of lobules or filaments covered with ciliated epithelium, and in which are very con- siderable vessels as branchial arteries and veins.(1) The branchiae are here always situated between the venous and arterial systems, so that a portion only of the whole blood is made to pass through the respiratory organs. It is possible that the two bundles of tentacles which are found with many Capitibranchiati, as infundibuliform,® or spiral® tufts, arc also res- piratory ; for their vibratory organs not only draw in food, but also pro- duce a constant change of the water. Other Capitibranchiati have distinct and exclusively respiratory organs in the cervical region, which are either dendritic,® or semi-pinnate.® With the Dorsibranchiati, nearly every segment of the body has branchiae upon both sides of its dorsal surface. These are so simple and rudiment- ary with the Ariceae, and Nereideae, that they consist only of simple lob- ules, exactly resembling the cirri of the feet.® Enchytraeus albidus, and others. Those canals thus situated remind one of the trembling organs of Rotatoria, connecting the two lateral canals with the cavity of the body 5 see above, § 138. 6 With Lumbricus terrestris, and its allie<J species, I have as yet been unable to find any ori- fices of the aquiferous canals. He rile also (Mul- ler's Arch. 1835, p. 580) has always found them looped upon themselves. They may however exist, although they have eluded the notice of Henle and myself, for the respiratory organs of Lumbricus are so difficult to study that there is yet no de- scription or figure giving any idea of their com- plexity 5 see the poor figures of Lumbricus ter- restris by Leo (loc. cit. p. 25, Tab. I. fig. 4), and Morren (loc. cit. p. 53, 148, Tab. XIV. XV.). Those of Hoffmcister, although more detailed, are scarcely less unsatisfactory (loc. cit. p. 15, Tab. I. fig. 35, 36). It now remains to inquire as to the relations existing between these aquiferous canals and the glands at their base which have been taken by many for mucous pouches. I cannot, for my own part, perceive that these glands with the Lumbricus terrestris, excrete any liquid what- ever upon the ventral surface. On the other hand, I have often seen escape from the back of this animal, a watery liquid which was only the con- tents of the cavity of the body, issuing through small orifices upon each side of the median line between the segments of the body. Although I do not know, yet I suppose, that similar orifices exist with the other Lumbricini, and thus, by these ori- fices and by those of the internal branchiae, the necessary renewal of water for these last, can take place. This hypothesis appears admissible since the cilia of the aquiferous canals always move in the same way. *l§ 159, note 7.] See, for many details on these parts, Gegenbaur (Ueber d. sogenannten 15* 7 These vesicular dilatations do not pulsate, and are undoubtedly analogues of the simple sinuses which communicate with the aquiferous canals of Nephelis vulgaris.* 1 These respiratory organs may be taken as analogous to the aquiferous vessels of the Lumbri- cini, which can be everted so that the internal cil- iated surface becomes external, and the external blood-vessels internal. 2 Serpula, and Pro tula. 3 Sahella. 4 Terebella; see Delle Chiaje, Mem. loc. cit. Tav. XLIII. fig. 1-5, Tav. XLV. fig. 2, 10 ; and Milne Edwards, Ann. d. Sc. Nat. X. 1838, p. 200, PI. X. XI. fig. 1. There are here on each side of the neck three multiramose, contractile branchiae which are placed close together. Into these a large portion of the blood of the median dorsal ves- sel enters by six lateral branches, while the re- maining portion passes on through the dorsal ves- sel to the tentacles and the borders of the lips. In each branchial tuft there are a simple artery and a vein placed side by side, which anastomose at its extremity in an arcuate manner. The returning blood from the six branchiae passes by as many veins into the median dorsal vessel, and the frequent strong contractions and dilatations of the branchiae, certainly very much aid the current. 5 Amphitrite ; see Pallas, Miscell. zool. p. 120, Tab. IX. fig. 1, 5, 0, 8, e, e ; Rathkt, Danzig. Schrift. loc. cit. p. 59, Taf. V. fig. 1, 3. Here the four semi-pinnate branchiae are upon both sides of the second and third rings of the body, and each lamella contains a tightly-closed vascular net- work. 6 The filaments of these branchiae are very short Respirationsorgane d. Regenwurms, in Siebold and Kblliker's Zeitsch. IV. p. 221). — Ed.