INKY SECRETIONS. 239 



peculiar property in the skin of the Cephalopoda, just de- 

 scribed, is given to them as a means of defence ; and the 

 conjecture seems to have been confirmed by some observa- 

 tions of Mr. Charles Darwin, which I shall transcribe for 

 your perusal. When at St. Iago, he was much interested, 

 on several occasions, by watching the habits of an octopus, 

 common in the pools left by the retiring tide. These ani- 

 mals, he says, escape detection by their cameleon-like power 

 of changing their colour. " They appear to vary the tints, 

 according to the nature of the ground over which they pass : 

 when in deep water, their general shade was brownish pur- 

 ple ; but when placed on the land, or in shallow water, this 

 dark tint changed into one of a yellowish green. The colour, 

 examined more carefully, was a French grey, with numerous 

 minute spots of bright yellow : the former of these varied in 

 intensity ; the latter entirely disappeared and appeared again 

 by turns. These changes were effected in such a manner, 

 that clouds, varying in tint between a hyacinth red and a 

 chestnut brown, were continually passing over the body." 

 " This cuttle-fish displayed its cameleon-like power both 

 during the act of swimming, and whilst remaining stationary 

 at the bottom. I was much amused by the various arts to 

 escape detection used by one individual, which seemed fully 

 aware that I was watching it. Remaining for a time mo- 

 tionless, it would then stealthily advance an inch or two, 

 like a cat after a mouse ; sometimes changing its colour : it 

 thus proceeded, till having gained a deeper part, it darted 

 away, leaving a dusky train of ink to hide the hole into 

 which it had crawled."* The Cephalopods then would seem 

 to be doubly armed ; for, when in danger, they are well 

 known to eject a copious black liquor through their funnel 

 or excrementary canal, as a means of obscuring the circum- 

 fluent water, and concealing themselves from all foes :f — 



" Long as the craftie cuttle lieth sure 

 In the blackc cloud of his thicke vomiture." J 



*■ Journal, iii. (>, 7. 



t Arist. Hist. An. ix. 37. Couch's Cornish Fauna, p. 81. 



X " The ink secreted in this bag has been said to be thrown out to conceal 

 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 con- 

 nected with the functions of the intestines." — Home's Comp. Anat. i. 376. 

 This opinion of Home's may seem to gain some support from an observation 

 of Lister's, who found the intestines and csecal appendages of a Loligo filled 

 with the ink. — Exer. Anat. tert. p. xxx. 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." M. d'Orbigny thinks it doubtful whether any of the Ccphalo- 



