184 Miscellaneous. 
therefore situated at the actual origin of these nerves. We can 
determine their seat by experiment. By inflicting localized injuries, 
either with red-hot iron or the scalpel, 1 have arrived at the following 
results :— 
Sub-esophageal centres—The destruction of the median sub- 
cesophageal lobe causes the paralysis of the chromatophores on the 
entire surface of the body, which remains absolutely pale. If the 
injury has only affected one side the paralysis likewise takes place 
on one side only, but on that opposite to the injury. There is 
therefore a manifest crossing of the nervous fibres in the thickness 
of the ganglion. 
Supra-cesophageal centres.—The removal of the cerebral calotte 
has no effect on the action of the chromatophores, provided that the 
injury does not extend to the optic nerves. If, on the other hand, 
the red-hot needle has reached the level of the optic nerve, it pro- 
duces, simultaneously with the dilatation of the pupil, the paralysis of 
the chromatophores of the injured side. It therefore appears that 
the chromatophores are under the influence of two centres, one for 
direct effects, the other for those which take place on the opposite 
side. After the destruction of the former it often happens that the 
chromatophores of the opposite side remain in a state of permanent 
dilatation. Now we know that in the normal condition the sensation 
in the Cephalopods may be expressed by the dilatation of the chroma- 
tophores and the intensely black coloration of the skin, or else by 
their maximum contraction and an extreme pallor. Are these two 
phenomena regulated by two different centres, a chromato-dilator 
and a chromato-constrictor? I have not succeeded in completely 
elucidating this point by experiments. 
Excitability of the centres.—This is demonstrated by direct stimu- 
lation. We can also operate upon it and modify it by physiological 
means: thus, it rapidly disappears after copious hemorrhage, and 
insensibly diminishes in animalsenfeebled by starvation and a sojourn 
in the aquarium. It increases under the influence of certain poisons. 
Strychnine and curari act upon it in a characteristic fashion : at 
each convulsive shock the chromatophores behave like the muscle ; 
their expanding movement commences and ceases s¢multaneously 
with the muscular shock. 
Form and characteristics of the movement.— The movement of the 
chromatophore is divisible into two stages :—(1) expansion, (2) con- 
traction. In anenfeebled animal the difference of duration between 
the two stages is so accentuated that we can register it in an indirect 
fashion, and in this way, by a special arrangement, I have obtained 
outlines which are as approximate as possible. If we compare these 
outlines with those of the contraction of the muscles of the mantle 
we find a striking resemblance. 
The radial fibres are muscles.—Of all the characters which have 
just been enumerated there is not one which cannot be referred to 
the properties of rapidly contractile muscles; it is, moreover, neces- 
sary to eliminate from henceforth the slowly contractile muscles of 
the skin. The peristaltic movements which are centred in the latter 
