SPERM WHALE’S FOOD. 
59 
totally dissimilar. Besides tentacula, the sepia is also 
provided with a pair of fleshy fins extending along the 
two sides of the body. The loligo has similar organs of 
a smaller size, and situated only at the extremity of the 
body which is opposite to the head. They have been 
regarded as the rudiments of true fins, which are organs 
developed in fishes, and which are supported by slender 
bones called rays, but no structure of this kind exists 
in the fins of the cephalopoda. In swimming, the 
organs principally employed by cuttle-fish for giving an 
effective impulse to the water are the tentacula. These 
they employ as oars, striking with them from behind 
forwards, so that their effort is to propel the hinder 
part of the body, which is thus made to advance 
foremost, the head following in the rear. They also 
use these organs as feet for moving along the bottom of 
the sea. In their progress under these circumstances, 
the head is always turned downwards, and the body up- 
wards, so that the animal may be considered as literally 
walking on its head ! 
“ The necessity of this position for the feet arises 
probably from the close investment of the mantle over 
the body ; for although the mantle leaves an aperture in 
the neck for the entrance of water to the respiratory 
organs, yet in other respects it forms a sack, closed in 
every part, except where the head, neck, and accom- 
panying tentacula protrude. 
“ In the calamary, as well as in the common sepia, 
two of the arms are much longer than the rest, and 
terminate in a thick cylindrical portion, covered with 
