§§ 256, 257. 



THE CEPHALOPODA. 



293 



Loligina. Their walls are composed of a dense web of cells, which, with 

 the Octopoda, contain round, violet nuclei, of a crystalline texture and 

 resembling entirely those found in the renal cells of the Gasteropoda/^^ 



//. Organs of Special Secretions. 



§ 256. 



The Ink-sac is an organ generally common with the Cephalopoda. It 

 is usually pyriform, situated upon the median line of the abdomen, and 

 often enveloped with a peritoneal layer of silvery lustre.''* Its apex points 

 forwards and upwards, towards the funnel. The walls of its generally small 

 cavity are cavernous,*^'' and secrete the well-known black pigment, which, 

 through contractions, passes into the funnel, and is then expelled, mixed 

 with the water of the sea, which is passing out of the body. The excretory 

 duct of this sac runs along the rectum, and terminates just behind the anus, 

 or opens into the rectum. ''^^ 



As an organ, also, of special secretion, ought to be regarded the com- 

 pletely-closed chambers found in the shell of the Nautilina ; for it is said 

 that their walls, like those of the natatory bladder of fishes, secrete a gas.<*' 



CHAPTER X. 



ORGANS OF GENERATION. 



§ 257. 



The Genital organs of the Cephalopoda are always distributed upon two 

 individuals, and present very remarkable peculiarities. 



uated at the inferior or lateral portion, separates 

 these bodies into two unequal divisions ; see Brandt, 

 loc. cit. Taf. XXXII. fig. 22, q. r. ; The Catal. of 

 the Physiol. Ser. II. PI. XXU. f. x. {Sepia) ; Delle 

 Chiaje, loc. cit. Tav. XCI. XCIII. XCV. XCVI. 

 (21, 23, 25, 26), {Loligo and Sepiola). 



9 Erdl {Varus, Erlauterungstaf. Hft. VI. p. 1) 

 has published an observation on the glandular na- 

 ture of these bodies, and the resemblance of their 

 parenchyma with that of the kidneys of Helix, all 

 of which I have been able to fully confirm. Nev- 

 ertheless, these organs demand further chemical 

 and histological investigation. 



1 This organ, which is entirely wanting with 

 Nautilus, and Hectocotylus, has an elongated 

 form with the long-bodied species, and is large 

 with those whose body is short ; see Wagner, Icon, 

 zoot. Tab. XXIX. fig. 20, h. i. (Octopus); Ferus- 

 sac. loc. cit. Argonauta, PI. I.^ fig. 2, 3 ; Brandt, 

 loc. cit. Tab. XXXII. lig. 1, 24, o. (Sepia). That of 

 Sepiola is quite remarkable in having an extraor- 

 dinary development in certain individuals, at par- 

 ticular seasons, without reference to the sexes. 

 There are then found two long bodies adherent by a 

 constriction to the sides of the otherwise simple ink- 

 sac. These lateral bodies are black, composed of a 

 glandular tissue continuous with that of the sac, 



25* 



and surrounded by a muscular layer. Peters 

 (Mailer's Arch. 1842, p. 329, Taf. XVI. fig. 1, b. 

 b. 8-10) has seen it contract regularly. With the 

 specimens preserved in alcohol the ventral surface 

 appears colorless. Grant appears to have been un- 

 aware of this increased development at certain 

 times with Sepiola, for he has attributed to them 

 in general a trilobed ink-sac (Transact, of the Zool. 

 Soc. I. p. 82). In the Sepiola figured by Delte 

 Chiaje (Descriz. Taf. XI. fig. i, 1.), the two lateral 

 lobes in question are very distinct. 



2 Delle Chiaje, Descriz. I. p. 74, Tav. XIII. fig. 

 1, 2. Tav. XVin. fig. 4 (Loligo, Octopus and 

 Eledone). 



3 This last case obtains with the IJoligina. 



i Owen (On the Nautilus, p. 47, or Isis, p. 39) 

 has, it is true, left undecided the question whether 

 these chambers are filled with gas or with liquid ; 

 but, according to Vrolik (Ann. of Nat. Hist. XII. 

 p. 174) the chambers of Nautilus pompilius really 

 contain a gas composed chiefly of nitrogen without 

 any trace of carbonic acid. These chambers resem- 

 ble, in many respects, the swimming blailders of 

 fishes, and, like them, serve, perhaps, to facilitate 

 the ascension and descensiou of these animals in 

 the water. 



