78 DR. R. E. GRANT ON THE ANATOMY OF SEPIOLA VULGARIS, 
also unusually large, and are peculiar in their dorsal position and mobility on the back, 
The body or mantle of the specimens obtained from our coast measures generally about 
six lines in length, and as much in breadth ; the head measures only four lines in length, 
and, from the magnitude of the eyes, is of equal breadth with the body ; the arms are 
of unequal lengths, the largest being about an inch long, and the shortest about a line 
less. The first or dorsal pair of arms are the shortest ; the second and fourth pairs are 
of equal lengths, and are alittle longer than the first pair; the third pair are the longest. 
This is the order of the comparative lengths of the arms most common in the Naked 
Cephalopods. The third and fourth arms on each side are connected to each other by 
a musculo-membranous fold, which extends to about a third of their length, and is 
covered by the skin and subjacent coloured spots. The arms, which are allied to those 
of Octopus in their length, agree with those of Loligo in being provided with numerous 
long pedunculated suckers. The suckers are of a globular form, and are placed on long 
thick conical muscular peduncles ; the suckers are arranged in two irregular rows on 
each arm, the bases of their muscular peduncles being in contact with each other, and 
placed alternately along the middle of the arms!. The general surface of the body has 
a pale reddish tint, and the spots, of a very dark purple colour, rare and small, extend 
over the mantle and dorsal surface of the fins, the head and arms, and partially over 
the tentacula. These spots are interspersed with a few patches of a larger size, and of 
the same deep purple hue. On removing a portion of the thick elastic epidermis from 
the back or head of this animal, it is easy to perceive that the spots, which remain un- 
injured on the surface of the subjacent skin and cellular tissue covering the muscles, 
are flat hollow vesicles containing a thin colourless fluid, in which are small portions of 
very dark coloured thick matter, imperfectly mixed with the thin fluid, and much re- 
sembling the ink of the animal. There appear to be a few pores in the parietes of these 
vesicles, of a dark colour, from which coloured matter can be pressed into the cavity of 
the vesicle, and moved to and fro in the colourless fluid without being dissolved by it. 
These coloured vesicles of Cephalopoda, situate in a cellular soft tissue covering the 
surface of the skin, occupy a place analogous to that of the rete mucosum, the usual seat 
of colour. 
The tentacula, about an inch and a half in length, thin and cylindrical to near their 
termination, where they expand a little and terminate in a point, proceed as in other 
Decapods from between the third and fourth arms on each side. They take their origin 
from the outer and fore part of the head, external to all the arms and to the disk which 
forms them by its subdivision ; in ascending they pass inwards between the bases of 
the arms just mentioned, which are the only two connected together by a membrane, 
and they thus appear to extend from behind these arms and their uniting membrane. 
When these two long and slender tentacula are retracted, they are concealed and pro- 
tected by the folds as by two sheaths ; and as none of the other arms are thus provided 
1 Plate XI. fig. 6. 
