^^6 NaiuraUUistorical CoUeciions. 



On the Chromophorous Globules of the Cephalopodous Mollusca — The entire 

 surface of the cephalopodous mollusca, and particularly the superior and lateral 

 portions of the body of these animals, are speckled by a great number of little 

 follicles, or globules, or little coloured circles, about the size of a grain of sand, 

 but varying in magnitude according to the species, and their degree of develop- 

 ment. Even the iris of these mollusca is richly ornamented with coloured fol- 

 licles, which add an additional splendour to its brilliant metallic lustre. 



Each of these spots is of a single colour. The principal tints which are found 

 ih the species inhabiting the Mediterranean, are yellow, red, brown, indigo, and 

 sky-blue, all varying in their degree of intensity. And the follicles may be di- 

 vided into as many orders as there are colours. 



The number of the orders of foUicles, which is found in each species, varies ; 

 in some they all exist ; in others we do not find so many ; but, except in the 

 Sepia Rondeletii, we never see less than two. They are distributed over the skin 

 of the animal, at equal distances ; and, although the number of follicles of each 

 colour be different, they are so combined that each part of the body of the ani- 

 mal is provided with them in an admirable proportion. 



The seat of these coloured follicles is the cutis, and especially the rete mucosum. 

 They are accordingly covered by the epidermis, which is smooth and transparent ; 

 they have no visible connection with any vascular system, nor with the part of 

 the body which is immediately below them. M. San Giovanni, who first accu- 

 rately described • these spots, considers them to be a system of organs, which he 

 has named the chromophorous or coloriferous organs. The colour which they 

 possess is not produced by any circulating or encysted fluid, but is inherent in 

 the tissue. 



But what is most remarkable in these spots is the alternate contraction and ex- 

 pansion which they exhibit on very slight irritation, even long after the death of 

 the animal. 



During life, when the animal is in a state of repose, the vesicles are contracted 

 and are not visible. When it is excited, by being touched with the hand, or 

 otherwise irritated, the coloured vesicles show themselves, and are instantly in mo- 

 tion, appearing and disapgearing with the velocity of lightning ; sometimes they 

 are like spots on different parts of the body, and sometimes like waves, which 

 rapidly move across its surface. M. San Giovanni states that each of these 

 vesicles is composed of a skin, having the structure of felt, and is provided with 

 a circular aperture, which can open and shut probably by means of a circular 

 muscle, and which enables us to see to the bottom. " And," he continues, 

 " their expansive and contractive power, during life, is owing to their particular 

 structure, which is subjected to the influence of the nervous system, with which 

 they are connected by means of delicate filaments, scarcely perceivable with the 

 aid of the microscope ; for every motion in them ceases when the skin is separated 

 from the body." Subsequently, however, to the publication of San Giovanni's first 

 memoir, more favourable opportunities for observation have occurred to our friend 

 Dr. Coldstream of Leith, who, in November 1826, read the result of his investi- 

 gations on the subject before the Royal Medical Society of Edinburgh. The 

 conclusions at which the author arrived, agreed in the main with those of the 

 other observers, with the important exception, that he found the spots to possess 

 motion even in pieces of the mucous coat which had been removed from the ani- 

 mal. Hence their dependence upon the nervous system was disproved, nor could 

 Dr. Coldstream, by the most careful microscopic examination, discover the slight- 



" This structure seems to have been first observed by Cams, in 1821. (Vide 

 Act. Acad. Nat. Cur. Vvl. XII. p. 320.) In 1822, Blainville alluded to it in 

 his Anat. Comp. ; but it was reserved for Dr. G. San Giovanni of Naj)les to 

 investigate minutely this peculiar system, which he described in 1824, in the 

 Giornale Encicl. di Napoli. A second memoir by the same observer has been 

 recently published in the Ann. des Sciences Naturelles, XVI. 315, the results 

 of which we give in the text.— Ed. 



