^247. 



THE CEPHALOrOI'A. 283 



or Pupil. The serous membrane just mentioned, which is spread over the 

 ocular bulb even to the papillary border of the iris, contains a particular 

 pigment of a silvery lustre, called the Argentea, and comparable to a Con- 

 junctiva. *^' 



With Onychoteuthis, Loligopsis, and allied genera, the anterior wall of 

 the ocular capsule is entirely wanting, and as there is also no cornea, the 

 crystalline lens is in direct contact with the surrounding medium (the water 

 of the sea). In the first of these genera, the free border of the capsule has, 

 in front, a deep fissure corresponding, perhaps, to a lachrymal canal.**'' 



The L'is is formed from the argentea, which is covered on its posterior 

 surface by a black Uvea, while its anterior surface often has chromatic cells. 



The pupil is usually of a transverse, or semilunar, rarely of a circular 

 form, and is capable of being completely closed.*'* Under the Argentea 

 extends a thin cartilaginous tunic — Sclerotica — which, behind, circum- 

 scribes the ocular bulb, and, in front, penetrates a certain distance into the 

 iris. It furnishes points of insertion for the muscles of the eye, and is crib- 

 riform behind for the passage of numerous filaments of the optic nerve. 



The cavity of the bulb is filled with a transparent, watei-y liquid which 

 takes the place of the vitreous body, and is contained in a very thin Hya- 

 Ididea. 



The Crystalline lens is spherical, and lodged in a deep depression of the 

 vitreous body. It is of a brownish color, and its anterior surface projects 

 through the pupil, so that the posterior chamber of the eye is only a small 

 circular space. As with the Vertebrata, this organ is composed of numer- 

 ous concentric layers, but has the remarkable peculiarity of being divisible 

 into halves, the anterior of which is less convex than the posterior, but 

 both are exactly joined together ; the borders of these halves are quite 

 bevelled, but are kept in place by the Ciliary body which arises from the 

 sclerotica and iris. One part of this ciliary body embraces the borders of 

 the lens, while the other penetrates between its halves as a thin, transparent 

 septum.® 



5 Zoolomists are not agreed upon the interpreta- PI. XXIV. fig. 2, d, 14 ; and Sepiola, PI. III. fig. 



tion to be put on this membrane. Krohn, and 5, 15. a, PI. VI. fig. 2. a, PI. IV. fig. 10. a. 

 Owen (loc. cit.), who regard the anterior part of 6 On account of this singular organization, COr- 



the ocular capsule as a cornea covered by a con- bignij (in Firussac, loc. cit. Introduct. p. 15) has 



junctiva, consider the cavity found behind it as a separated, under the name Oigopsidis, the genera 



large anterior chamber, filled with a Humor ague- mentioned in the text from the other Loligina which 



us. Cuvier, fVharton Jones (loc. cit.), and J. he caWs Myopsides. The segment of the border of 



Müller (in his Arch. 1836, Jahresb. p. 91), re- the capsule, and which is wanting with Loligopsis, 



gard the capsular cavity with its serous membrane, is spoken of as a Sinus lacrymalis in Fenissac, 



as a closed conjunctival sac ; so that the transpa- loc. cit. Onychoteuthis, PI. III. fig, 1, PI. III. tig. 



rent convexity of the capsule is not a cornea, but 2, PI. XII. fig. 4, 13, PI. XIV. fig. 1 ; Ommastre- 



a continuous closed eyelid. Moreover, as there pkes, PI. I. tig. 15, PI. 11. fig. 3, 11. 

 are often found two rudimentary eyelids in the 7 The pupil is not circular except with Onycho- 



eyes of Cephalopoda (Mayer, Analekt. f. vergleich, teuthis, Ommastrephes, and Loligopsis. 

 Anat. Hft. I. p. 52, Taf. IV. fig. 6-11), this trans- The upper papillary border, usually convex 



parent convexity may be regarded as a third lid with the other Cephalopoda, is often prolonged as 



or a nictitating membrane adherent throughout ex- a Velum or Operculum pupillare. With Sepia, it 



cept at the point of the opening. Many anatomists, is often bilobed after death ; see the figures of F^- 



and especially Cu wer, and Owen, have not no- russac, loc. cit. a.nd Delle C/jio/e, Osservaz. anat. 



ticed this opening of the ocular capsule. But De loc. cit. Tav. IX. fig. 1, 2, 3. 



Blainville (Princip. d'Anat. comp. I. p. 444, and 8 For the lens and the ciliary body, see Huschke, 



Diet. d. Sc. Nat. XLVIII. p. 262) mentions it with Comment, de pectine in oculo Avium, 1827, p. 9, 



Loligo, Octopus, and Sepia ; and Wagner (Ana- fig. 11, and Delte Chiaje, Descriz. &c. Tav. V. fig. 



lekt. &c. p. 53) has described it carefully. 18, and Tav. XIX. fig. 6-8. Although Mayer 



In the large work of Firussac, it is often fig- (Analekt. loc. cit. p. 54) declares that this lens has 



ured under the name of Orifice lacrymal ; see a capsule, yet I am undecided on this point, for the 



Loligo, PI. XX. fig. 7, PI. XXIII. fig. 5, a. 17, other anat/cauists are silent.* 



* [§ 247, note 8.] The microscopic structure of These fibres however are more than twice as small 

 this lens corresponds also with that of the Verte- as those of any of the Vertebrata I have examined, 

 brata — that is, composed of delicate tubes or fibres. — Ed. 



