CUTTLEFISA. 403 
within the mantle cavity lie the anus and the openings of 
the nephridia and genital duct. : 
The true orientation of the different regions in Sedza is 
not obvious. If the “arms” surrounding the mouth be 
divided portions of the anterior part of the “foot,” the 
ventral surface is that on which the animal rests when we 
make it stand on its head. We can fancy how the “foot” 
of a snail might grow forward and surround the mouth, so 
as to bring that into the middle of the sole. Then the 
visceral mass has been elongated in an oblique dorso- 
posterior direction, so that the tip of the shield, directed 
forward when the cuttle jerks itself away from us, represents 
in anatomical strictness the dorsal surface tilted backwards. 
(As above noticed, the animal may also swim with foot and 
mouth in front.) The side of lighter colour, marked by the 
mantle cavity and the siphon or funnel, is postertor and 
slightly ventral; the banded and more convex side, on which 
the cerebral ganglia lie in the head region, and on which 
the shell lies concealed in the visceral region, is anterior 
and slightly dorsal. 
Skin.—There are numerous actively changeful pigment 
cells or chromatophores lying in the connective tissue 
beneath the epidermis. Each cell is expanded by the 
contraction of muscular cells which radiate from it, and 
-contracts when these relax. It is probable that these 
chromatophore cells have some protoplasmic spontaneity 
of their own, but the controlling muscular elements are 
also affected by nervous impulses from the central ganglia. 
As the cells dilate or contract, the pigment is diffused or 
concentrated, and the colours change. The animal’s beauty 
is further enhanced by numerous “‘iridocysts” or modified 
connective tissue cells, with fine markings which cause 
iridescence. 
Muscular system.—The cuttlefish is very muscular, 
notably about the arms, the mantle flap, and the jaws. 
Many of the muscles show double oblique striping. The 
animal seizes its prey by throwing out its two long arms, 
which are often entirely retracted within pouches. With 
great force it jerks itself backwards by contracting the 
mantle cavity, and making the water gush out through the 
pedal funnel. This mode of locomotion is very quaint. 
