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.

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    The Acalephae have no true digestive tube. But, as such, has been regarded a system of vascular cauals filled with water, and which, de- parting from the stomach, traverse the whole body. But these, although sometimes seen to contain faeces, seem to belong more properly to the respiratory system.® In none of the Acalephae has there been found anything like an hepatic organ.(10) CHAPTER VI. CIRCULATORY SYSTEM. § 62. Until lately, the longitudinal and circular canals which, in some Acale- phae, are spread out through the entire body, have been regarded as belonging to a vascular, sanguineous system. But more recently these have properly been considered as aquatic-respiratory organs, there having- been found, moreover, other vessels of exceedingly thin walls, and of a sanguineous nature. These last constantly accompany and surround in a tubular manner the aquiferous canals; and it is quite rare that small branches are distributed to the general parenchyma. The delicate walls of these vessels have neither longitudinal nor circular fibres, neither are they lined with ciliated epithelium. They circulate a required to thoroughly settle this point. See below, the respiratory organs. See also Hollar d, who unhesitatingly regards the canals, which, with Ve- le.Ua, communicate externally by a central opening, as a digestive cavity, and thinks he has observed in their walls brownish spots representing the hepatic cells ; see Ann. d. Sc. Nat. III. 1845, p. 249, PI. IV. bis. 9 The aquiferous canals of the respiratory sys- tem having been regarded as intestinal tubes, their orifices, which in the Ctenophora are situated at the extremity of the body, and in the Discophora upon the borders, have been considered as anal openings 5 and especially so, since in these two orders, accidental faeces in these canals are expelled through these orifices. See Will, loc. cit. p. 28, * [§ 61, note 9.] Upon the nutritive system of the Acalephae, see Forbes (loc. cit. p. 4), but especially Agassiz (loc. cit.), who has studied the subject with conscientious care. There is no dis- tinction between the alimentary canal proper and the vascular system, for the one opens by large tubes into the other. The Acalephs, therefore, cir- culate chyme, and here we have the rudest form of circulation. If this idea is once well considered, the relations of their nutritive apparatus in general will be quickly appreciated. The variations in the shape and form of the di- gestive apparatus are wide and numerous,'but and Ehrcnberg, Abhandl. d. Berl. Akad. 1835, p. 189, Taf. I. IV. fig. 2, z* 19 Acalephm possess an extraordinary digestive power, which is the more singular as no secretory organ has been found on the sides of their stomach. Mertens (MYm. d. l’Acad. de St. Petersburg, loc. cit. p. 490, Taf. I. fig. 5, 6, a. ; and p. 518, Taf. VIII. fig. 4, Taf. IX. fig. 1, f.), however, affirms to have seen in Cestum and Cydippe four vessels in this situation, which are perhaps hepatic organs. The orange-colored cords found upon the sides of the stomach of Stephanomia, and which Milne Edwards (Ann. d. Sc. Nat. XVI. p. 222, PI. VII. IX. X.) has taken for genital organs — may they not also be hepatic organs ? f their importance is rather in Zoology. See Agas- siz for the details of Sarsia, Hippocrene, Tiarop- sis, Staurophora, Pleurobranchia, Bolina.— Ed. f [§ 61, note 10.] Kblliker (Siebold and Kolli- ker^s Zeitsch. IV. lift. 3,4, p. 313) has observed with Velella and Porpita a glandular mass, correspond- ing most probably to a liver. It had before been regarded as such by Belle Chiaje, but Kblliker has given it a special description. It consists of a brown mass which communicates with the bottom of the stomachal cavity by branched, anastomosing ducts. — Ed.