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.

    68/482 (page 64)
    their body, button and tongue-like organs, which, as they are connected with neighboring ganglia, may well be regarded as organs of sense. Their essential structure is a membranous capsule, containing a clear liquid, in which are suspended crystalline corpuscles. These organs, having sometimes a red pigment, have been taken for eyes; but, as most of them are without pigment, and-as the crystalline corpuscles behave in acid like the Otolites of the higher animals, they have more recently been better designated as organs of hearing. The eight marginal, tongue-like bodies, found upon the disc of Medusa aurita, have been regarded as eyes.® The sole fact for the support of this opinion is the presence of pigment; for the small hexagonal crystals, irreg- ularly scattered in the interior of these bodies, would scarcely allow them to refract the light like a crystalline lens. The Ctenophora have only a single organ of this nature, and which is situated near the ganglion at the posterior end of the body. It has been regarded both as an eye and as an organ of hearing.® With many Discophora, these organs appear as pale-yellow, or even colorless marginal corpuscles, having more or less calcareous bodies.® It is yet doubtful whether the otolites of the Acalephae perform the same movements as those of the acephalous and gasteropod mollusca.® 1 These marginal corpuscles, already observed in the Medusae by Gaede (BeitrSLge zur Anat. u. Phvs. der Medusen, 1816, p. 18, 28), and by Rosen- thal (Zeitsch. f. Physiol. Bd. I. Hit. 2,1825, p. 326), were first described as eyes by Ehrenherg. See Muller's Arch. 1831, p. 571, and Abhandl. d. Berl. Akad. 1835, p. 190, Taf. IV. V. 2 Milne Edwards has called this body, in Lesu- euria vitrea and Beroa Forskalii, “ Organe ocu- liforme (Ann. d. Sc. Nat. loc. cit. p. 206, 211, PI. IV. 'fig. 1, k. and PI. V. fig. 4, i.). According to Will (Froriep's neue Not. No. 599, p. 67, ami Horse tergest. p. 45, Taf. I. fig. 2, 4, 20, b.), the red pigment of these organs is entirely wanting in Beroa, Eucharis and Cydippe, while the hexago- nal calcareous corpuscles are very numerous — a fact leading him to conclude that these organs are auditory vesicles. • 3 According to Wagner (Ueber den Bau, &c., and Icon. zoot. Tab. XXXIII. fig. 31, g. 23, c. and 25), these corpuscles are pale-yellow in Pelagia noctiluca, and colorless in Oceania, Cassiopea and Aurelia. In Cephea, Will has observed only pale-yellow corpuscles, filled with crystals. And, according to him (loc. cit. p. 64, 68), the colorless pedunculated marginal vesicles of Polyxenia leu- costyla contain, each only a single round otolite, while those of Cytaeis potystyla contain numbers, colorless or yellow, and of irregular forms. He has also observed (loc. cit. p. 72, Taf. II. fig 9, 10) that in Geryonia the number of these otolites varies from one to nine. Milne Edwards (Ann. * f § 560, note 4.] The organaof sense of the Aca- lephae have been the objects of much study of late, and to Agassiz we are indebted for the most minute researches on these obscure points. He has shown the eye-specks to be undoubted organs of sense, from their connection with the nervous system. With the naked-eyed Medusae, he regards them light-perceiving instead of auditory organs. In regard to the single organ found with the Cteno- phora, and which Frey and Leuckart have re- d. Sc. Nat. XVI. p. 196, PI. 1^ e.) has observed upon the margin of the disc of Aequorea violacea vesicles containing two or three spherical corpus- cles, and which, probably, are auditory organs. According to Sars (Wiegmann's Arch. 1841, Th. 1. p. 14, fig. 60), and Will (loc. cit. p. 75, Taf. II. fig. 21, A. B.), these marginal corpuscles are found upon young Medusae belonging to Ephyra. 4 Will has never observed with the Otolites of Acalephae similar movements to those of mollusca. Kolliker (.Froriep's neue Not. No. 534, p. 82) has observed vibratile cilia upon the inner surface of the marginal corpuscles of Pelagia, Cassiopea, R/iizostomum and Oceania, which are pyriform, and contain many calcareous crystals. In the pedunculated vesicles of Geryonia, which contain only a single crystal, these cilia are absent. In none of the Medusae has he found collections of pigment, and in Oceania (nov. spec.) only he has observed a mass of brown pigment cells upon the external and superior surface of the base of these corpuscles 5 in the centre he perceived a round transparent body, and upon the upper surface a circular opening, so that the whole closely resem- bles an eye, there being, moreover, a kind of pupil- lary opening, and the traces of an optic nerve from a ganglion. According to the observations of Frey and Leuckart (Beitr. &c. p. 39), the group of otolites contained in the auditory organ of a Cydippe per- form oscillatory movements, due evidently to vibra- tile cilia situated on the auditive capsule.* cently declared to be of an auditory nature, ho remarks : “ I am inclined to consider this organ, or this speck, as something similar to the central col- ored speck which occurs in the middle of the disc in Discoid Medusae, and which is particularly dis- tinct in young animals soon after they have been detached from the polyp-like stem on which they grew, as a remnant of the connection which exists between the mother-stem and its progeny in those Medusae which multiply by alternate generations.”