622 Natural History of Molluscous Animals:—^ 



experiments with other pieces of the spotted membrane, and 

 always with similar results. At the end of nearly two hours 

 from the time when some of them were removed from the 

 animal, the spots were dilating; but, in the course of a few 

 minutes afterwards, motion finally ceased." * 



4. It has been conjectured, that the peculiar property in 

 the skin of the Cephalopoda, just described, is given to 

 them as a means of defence : but the conjecture seems to 

 have been hazarded merely to satisfy the craving wish, which 

 we all entertain, to know the uses or final cause of things 

 that pass under our observation ; for I know no experiments 

 or facts that tend to give it stability: and, if the opinion is 

 just, then the cuttles would seem to be doubly armed; for, 

 when in danger, they are said to eject a copious black liquor 

 through their funnel or excrementary canal, as a means of 

 obscuring the circumfluent water, and concealing themselves 

 from all foes : — 



" Long as the craftie cuttle lieth sure 

 In the blacke cloud of his thicke vomiture." "f* 



This inky fluid is a very remarkable secretion, produced in 

 a bag that lies near the liver, and sometimes even embosomed 

 in it, and communicating with the funnel by means of its own 

 excretory duct. The interior of the bag is not a simple 

 cavity ; it is-filled with a soft cellular or spongy substance, in 

 which the ink is diffused. This has no relation or analogy 

 with bile, as Munro believed ; but it is a peculiar secretion, 

 somewhat glutinous, readily miscible with water, and variable 

 in point of shade, according to the species of cephalopode 

 from which it comes; so that, as Dr. Grant remarks, a 

 more intimate acquaintance with this character might be 

 useful in tracing relations among the different species. The 

 colour of the ink in jLoligo sagittata * is a deep brown, 



* Edin. Journ. Nat. and Geogr. Science, vol. ii. p. 296. The paper from 

 which the above extract is taken contains the best account which has yet 

 been published of these coloured vesicles, or " chromophorous globules," as 

 they have been termed. The reader may also consult the Edin. Phil, 

 Journ.y vol. xi. p. 422. 



\ " The ink secreted in this bag has been said to be thrown out to con- 

 ceal the animal from its pursuers ; but, in a future lecture, I shall endeavour 

 to show that this secretion is to answer a purpose in the animal economy- 

 connected with the functions of the intestines." (Home's Comp. Anat.y vol. i. 

 p. 376.) Dr. Coldstream, in a letter to the author, detailing the manners of 

 Octopus ventricosus in captivity, says, " I have never seen the ink ejected, 

 however much the animal may have been irritated." I have, however, 

 been told by our fishermen, that they have seen this species eject the black 

 liquid, with considerable force, on being just taken from the sea. 



% Sir R. Sibbald says that the ioligo, or hose-fish, besides its ink, has 

 another purple juice. {Scot. lUust.y vol. ii. lib. 3. p. 26.) I find no men- 

 tion of this in any other author. 



