V>4 --36, 257. THE CEPHALOPODA. 293 



Loligiiia. Thoir 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 Grasteropoda.'^' 



//. Orga^is 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 and surrounded by a muscular layer. Peters 



these bodies into two unequal divisions ; see Brandt, {Mal/er's Arch. 1842, p. 329, Taf. XVI. ficr. 1, b. 



loc. cit. Taf. XXXII. fig. 22, q. r. ; The Catal. of b. 8-10) has seen it contract regularly. With the 



the Physiol. Ser. II. PI. XXII. f. x. (iiepia) ; Delle specimens preserved in alcohol the ventral surface 



Ckiaje, loc. cit. Tav. XCI. XCIII. XCV. XCVI. appears colorless. Grajii appears to have been un- 



(21, 23, 25, 26), {Loligo and Sepiola). aware of this increased development at certain 



9 Erdl (Carus, Erlauterungstaf. Hft. VI. p. 7) times with Sepiola, for he has attributed to them 



has published an observation on the glandular na- in general a trilobed ink-sac (Transact, of the Zool. 



ture of these bodies, and the resemblance of their Soc. I. p. 82). In the Sepiola figured by Delle 



parenchyma with that of the kidneys of Helix, all Chiaje (Descriz. Taf. XI. fig. 4, 1.), the two lateral 



of which I have been able to fully confirm. Nev- lobes in question are very distinct, 



ertheless, these organs demand further chemical ^ Delle Chiaje, Descriz. I. p. 74, Tav. XIII. fig. 



and histological investigation. 1, 2. Tav. XVIII. fig. 4 (Loligo, Octopus and 



1 This organ, which is entirely wanting with Eledone). 



Nautilus, and Hectocotylus, has an elongated 3 This last case obtains with the Loligina. 



form with the long-bodied species, and is large 4 Owen (On the Nautilus, p. 47, or Isis, p. 39) 



with those whose body is short ; see Wagner, Icon, has, it is true, left undecided the question whether 



zoot. Tab. XXIX. fig. 20, h. i. {Octopus) ; Firus- these chambers are filled with gas nr witli liquid ; 



sac, loc. cit. Argonauta, PI. 1." fig. 2, 3 ; Brandt, but, according to f-'rolik (Ann. of Nat. Hist. XII. 



loc. cit. Tab. XXXII. lig. 1, 24, o. {Sepia). That of p. 174) the chambers of Nautilus ponipilius really 



Sepiola is quite remarkable in having an extraor- contain a gas composed chiefly of nitrogen without 



diiiary development in certain individuals, at par- any trace of carbonic acid. These chambers resem- 



ticular seasons, without reference to the sexes, ble, in many respects, the swimming bladders of 



There are then found two long bodies adherent by a fishes, and, like them, serve, perhaps, to facilitate 



constriction to the sides of the otherwise simple ink- the ascension and desceusion of these animals in 



sac. These lateral bodies are black, composed of a the water, 

 glandular tissue continuous witli tliat of the sac, 



25^ 



