282 THE CEPHALOPODA. <§, 247. 



The auditory organs of Nmitilus are somewhat different. They are 

 widely separated from each other, and situated in the prolongations of the 

 cephalic cartilage which extend in front ; they consist of a very long, nar- 

 row labyrinthian cavity containing a homogeneous, thick liquid without 

 otolites. <^> 



§247. 



The Eyes of the Cephalopoda are very highly developed and dispro- 

 portionately large. *^' Although resembling very much those of the Verte- 

 brata, yet they differ from them in many respects.*'-' With the Octopoda, 

 and Loligina, each eye has an ocular Bulb and a Capsule. 



The capsule is formed by the cartilaginous orbit, and by a fibrous mem- 

 brane attached to the borders of this last, and is blended externally with 

 the cutaneous envelope. This envelope, in the form of a circular swelling, 

 covers the eye, and, being thin and transparent, takes the place of a Cornea, 

 — a part which, properly, does not exist with the Cephalopoda. ''' 



The circular swelling often has, above and below, a semilunar fold of 

 skin containing muscular fibres, which, upon contraction, cover the con- 

 vexity of the eye like an upper and under lid. The ocular bulb, contained 

 in this capsule, is round and a little flattened in front ; and, as it is not ad- 

 herent to its capsule in front nor upon the sides, there is a free space, 

 which, from the absence of a cornea, would coincide with the anterior 

 chamber of the eye.'*' In most cases, this space contains a transparent 

 liquid, and is lined by a serous membrane covering not only the posterior 

 surface of the anterior part of the capsule, but also the anterior surface of 

 the bulb. It is remarkable that this same space, which contains in part 

 the anterior chamber, communicates, externally, by a circular orifice which, 

 with the Octopoda, is covered by the upper lid, and with the Loligina, is 

 situated upon the anterior border of the cutaneous fold which takes the 

 place of the cornea. Internally, this space can be closed by a kind of fold 



disc, concave on one side, and very convex and 1 The largest eyes are found with the Loligina ; 

 sometimes even conical, on the otlier Scarpa, loc. the smallest with the Octopoda. 

 cit. Tab. IV. fig. 9, and fVeber, De Aure et Audi- 2 For the structure of the eyes of Cephalopoda, 

 tu, p. 11, Tab. II. fig, 8, (Octopus) ; also Delie see, beside Cuvier, Mem. p. 37, PI. II. fig. 5, and PI. 

 Chiaje, Memor. Tav. LVIII., and Descriz. &c. Tav. Ill, fig. 7, and Owen, Cyclop. I. p. 551, fig. 234, 

 XII. fig. 15, 19, 23, 24, {Octopus and Eledone). — Massalien, Descript. oculorum Scombri Thynni 

 With Octopus, they have a crystalline structure ; and Sepiie, Diss. Berol, 1815, p. 10 ; Soeinmer- 

 but with Eledone, where they are very flat and rin^, De Oculorum hominis aniraaliumque sectione 

 colored brown on one of their surfaces, they con- horizontal!, p. 76, Tab. III.; De Blai7ivi/le, Princ. 

 sist of a soft limeless substance, — often rendering d' Anat. comp. p. 441 ; Mayer, .\nalekt. f. vergleich. 

 in vain the search for them in specimens long pre- Anat. lift. I. p. 52 ; Krohn, Nov. Act. Acad. Leop. 

 served in alcohol. Carol. XVII. Pt. I. p. 339, Tab. XXVI., and XIX. 

 The irregular otolites of the Loligina, which ap- Pt. II. p. 43 ; Wharton Jones, Lond. and Edinb. 

 pear bristling with points and serratures (Scarpa, Philos. Mag. 1836, Jan'y, or Froripp\i Notiz. 

 loc. cit. Tab. IV. fig. 8, and Delle Chiaje, loc. XLVIII. p. 2, fig. 1-3 ; Delle Chiaje, Descriz. 

 cit. Tav. LVIII. (12) fig. 13, 14, 16, 25, 26, (Se- &c. I. p. 70, Tav. XIX. and XXIX. also Osservaz. 

 pia and Loligo),), have the aspect, under the mi- Anatom. su I'occliio umano 1838, Tav. IX. fig. 1- 

 croscope, of an aggregation of very flue, acute II; f'a/enim's ideal section of an eye of a Cepha- 

 prisms, the points of which turn inwards (Carus, lopod, in IVa^ner's Icon. zoot. Tab. XXIX. fig. 

 Lehrb. d. vergleich Zoot. I. p. 358). 42 ; and John Power, Dublin Jour, of Jled. Sci- 

 fi See Valenciennes, loc. cit. p. 291, PI. VIII. ence, XXII. 1843, p. 350. 

 fig. 2, No. 3, and PI. IX. fig. 4, 5, a. He has 3 Krohn, Valentin, and others, admit the exist- 

 seen it supplied with nerves coming directly from ence of a particular horny substance situated be- 

 the brain. Owen (Qn the Cephalop. with cham- tween the cutaneous layers of the anterior part of 

 bered shells, p. 10) took them for venous sinuses, the ocular capsule. 



and could not admit that they were auditive or- -4 Treviranus (Vermischte Schrift. III. p. 154; 



gans, since they contained no otolites. But it says he has observed a thin, transparent, but solid 



might be argued that these otolites are limeless like membrane, placed directly in front of the lens, and 



those of £/edottc, and may, therefore, dissolve and continuous with the conjunctiva (Argentea), thus 



entii'ely disappear after death. forming a completely-closed anterior chamber ; but 



this statement requires confirmation. 



