Miscellaneous. 183 
On the Nature of the Movement of the Chromatophores of 
Cephalopods. By M. C,. Pursaurx. 
It is stated by P. Bert, in his important memoir on the physiology 
of the cuttle, that the movement of the chromatophores is due to 
dilatatory muscles with rapid contractile power. MM. Pelvet and 
Frédérick were the first to support this view with experiments. 
Another theory, which owes its origin to anatomical observations, 
considers these movements to be of an amoeboid nature. It was 
advanced by Harting, and has been maintained by MM. Raphael 
Blanchard, P. Girod, and quite recently by M. Joubin. However, 
the latter author reconciled the theories by admitting the former for 
the young and the latter for the adult chromatophore, and, as a 
corollary, the transformation of muscular into connective fibres. 
The theory of P. Bert is the only rational one. It was to demon- 
strate the justice of it that I undertook a series of investigations at 
the zoological station of Arcachon, where, thanks to MM. Viallanes 
and Jolyet, | found the material necessary for my task. 
Three kinds of movements are distinguishable in the chromato- 
phores. : 
1. Tremulous movements.—In a living Cephalopod, in a state of 
rest, the chromatophores are constantly agitated by little shocks, 
which are scarcely visible; it is like an incessant and rapid 
trembling, and this gives the skin of Cephalopods its characteristic 
appearance. These movements are under the control of the nervous 
system ; they disappear as soon as the pallial nerve is divided or the 
chromato-motor ceutres are injured. In that case the chromato- 
phores diminish still further in diameter and the skin attains its 
maximum degree of paleness. 
2. Undulating movements.—These do not set in, as a general rule, 
until after death. They consist in the maximum expansion followed 
by the contraction of the chromatophores. ‘Their characteristic 
feature is that they commence at one or several points and radiate 
thence in all directions, to reproduce themselves in an irregular and 
disordered fashion. They are due to the direct stimulation of the 
skin, and persist for a long time after death. 
3. Movements of functional activity.—These occur in the living 
animal only, and serve it asa means of defence. They are the result 
of reflex actions, which depend entirely on the central nervous 
system. Accordingly the section of the pallial nerve at the neck 
suffices to render them impossible in the portion of the body inner- 
vated by this nerve. ‘The galvanization of the peripheral extremity 
of this nerve provokes the dilatation of the chromatophores, which 
remain in a state of expansion so long as the stimulus continues. 
It is a veritable tetanization. It is produced and ceases simulta- 
neously with that of the muscles of the mantle. A single stimulus 
induces a transitory dilatation, which appears and terminates simulta- 
neously With the muscular shock. 
Chromato-motor nervous centres.—If we stimulate the central 
extremity of the pallial nerve we obtain the dilatation of the chroma- 
tophores of the opposite side. The centre of the reflex actions is 
