112 
POPULAR SCIENCE REVIEW. 
each end. Its summit (fig. 1 /) projects upwards above the top 
margin of the mantle ; its lower end opens into the pallial 
chamber. 
The arms are ten in number :* eight of these are of moderate 
length ; but two (called tentacles) are very long, retractile, and 
expanded at their ends (fig. 1 t and i'). 
Each arm, on its inner surface, is furnished with a number 
of suckers {acetahula), each one of which may be compared to 
a small cupping glass on a short stalk. 
Each acetabulum has a toothed horny margin, and its interior, 
when it is in a passive state, is nearly filled by a muscular 
papilla, or small fleshy mass. This papilla, however, can be 
contracted, and then occupies but a small space at the bottom 
of the cup. 
The cuttle-fish seizes objects in this fashion. First it 
closely applies the horny margins of the acetahula to the 
surface of the object seized. It then immediately contracts the 
papillae, and thus produces a vacuum inside each acetabulum, 
causing a most intimate adhesion by atmospheric pressure. 
Yet, in spite of the excessive tenacity of the grasp produced by 
the simultaneous action of hundreds of acetahula, the cuttle-fish 
can let go its hold in a moment, by simply relaxing the con- 
traction of the papillae, and allowing them to return to their 
passive condition. The male cuttle-fish has a certain space on 
one of its arms devoid of suckers. * 
On each side of the head there is a very large and brilliant 
eye, constructed on essentially the same plan as the human eye, 
except that there is no iris, its place seeming to be supplied by 
a deep groove which runs round the lens of the eye. Moreover, 
the transparent coat outside the lens, i.e. the cornea^ is per- 
forated, thus presenting permanently a condition which tran- 
sitorily exists in higher animals. 
When the cuttle-fish is irritated, peculiar flushes of colour 
pass over its skin. This appearance is produced by the pulling 
open, by the contraction of very small muscular fibres, of little 
bags of bright coloured and differently coloured pigment, and 
which little bags when in their contracted state appear as small 
dark specks on the skin. These little bags are termed chroma- 
tojjJcoreSy i.e. “ colour-carriers.” 
Everybody knows the cuttle-bone. Its technical name is 
sejAostaire. It is a cellular, calcareous substance, the use of 
which is problematical, as, although it is light (with its inter- 
spaces filled with air), it can hardly have much effect as a float. 
Perhaps it serves rather as a point (Vappui, or possibly as a 
• in the Poulpc, and certain other forms, there are but eight arms, 
whence such are termed Octopods. 
