236 COLOUR OF CEPHALOrODA. 



Naturalists have been long acquainted in some degree with 

 these singular phenomena. Pliny tells us that the cuttle-fish 

 change their colour through fear,* adapting it, cameleon-like, 

 to that of the place they are in ; and some expedience-dog- 

 matists have meanly recommended us to imitate their accom- 

 modating quality — 



" Apud homines cum eris, tibi in mentem veniat polypi, 

 Ad saxa variari nativum colorem corporis. "t 



None of the older authors, however, attempted to investi- 

 gate their cause ; hut, of late, several theories have been 

 offered, and two of these are founded on a minute inquiry 

 into the structure of the vesicles. Cuvier said, conjecturally, 

 that the appearances were dependent on the effusion of a 

 coloured fluid in the areolar tissue of the skin ; J and Pro- 

 fessor Grant refined upon this hypothesis, by supposing the 

 fluid to pass repeatedly to and from the minute vesicles : § 

 but this conjecture has been apparently disproved, for the 

 spots have no connection with any vascular system, nor do 

 the vesicles contain any encysted fluid. Dr. G. San Gio- 

 vanni, of Naples, an intelligent comparative anatomist, offered 



* Hist. Nat. ix. 46. 



+ Plutarch compares flatterers to the Polype. In his Oat. de Patient, et 

 Tolerant., he says, " Nor must the wiles and fraud of the Polype be passed 

 over in silence. To whatever rock it adheres it imitates and assumes its 

 colour, and thus many fishes while swimming strike against the polype as 

 against a rock, and become the prey of its craftiness. Similar in manner 

 are those who always frequent the company of those who have power and 

 command, and who so accommodate themselves to times and occasions, that 

 they never remain permanently of one opinion, but carry themselves hither 

 and thither and change their opinions at any one's will and pleasure." 

 Clearchus's advice is, — 



"Polypi, mi fili, Amphilocles heros, mentem habe, 

 Et ad quorum gentem veneris, te iis accommode." 



I Mem. i. 7. 



§ Edinb. New Phil. Journ., xvi. 313. — This opinion is also adopted by 

 H. Milne-Edwards, who seems to rest it upon experiments which are cer- 

 tainly at variance with those of Dr. Coldstream. H. Milne-Edwards says, 

 " The skin of these animals is furnished with a number of differently-co- 

 loured spots, which alternately appear and disappear ; and if a portion is put 

 under a microscope, it may be perceived that these changes depend on the 

 contraction of small vesicles filled with a coloured liquid, which reach from 

 the surface of the skin to a considerable depth. When one of these spots 

 appears, the liquid corresponding here to the pigment in the other case is 

 propelled towards the superficial part of the vesicle, and there displays 

 itself ; whilst during its disappearance it is forced into the deeper parts by 

 the contraction of this superficial point itself, which then becomes almost 

 invisible." — Edinb. New Phil. Journ. xvii. 319. 



