a rare Species of Octopus Jrom the Firth of Forth, 313 



arms from the mouth 12 inches; extent of the muscular web between 

 the arms 3 inches ; breadth of the web between each pair of arms 

 4 inches ; breadth of the head at the eyes 2^ inches ; external aper- 

 ture of the eyelids when expanded into a circle only ^th of an inch. 

 The coloured spots of the skin are of a deep reddish brown colour. 

 In the cirrhosus, Lamarck states that they are of a bluish grey co- 

 lour. In the 0. vulgaris they are brown. Lamarck states that the 

 whole skin of the moschatus is white, but Carus has represented it 

 spotted with red. In the ventricosus they are so minute and crowd- 

 ed together on the back, as to be almost undistinguishable without a 

 lens ; the largest are about the tenth of a line in diameter, and be- 

 tween these are crowded others infinitely smaller. On the fore 

 parts of the body they are few, and placed at greater distances from 

 each other. The colour is of different intensity in different spots, and 

 even in different parts of the same spot. They are confined to a 

 thin layer on the outer surface of the true skin, which may be com- 

 pared to the rete mucosum of the higher animals. When a part of 

 the surface is plunged into boiling water, the coloured superficial film 

 is easily removed. In the living state, the spots appear and disappear 

 in rapid succession, as in other cephalopodous animals. In a young 

 specimen of the ventricosus only about 4 inches in total length (now in 

 the Museum of the University), which I kept alive for some hours in 

 a basin of sea water, I observed, that, when the surface of the body 

 was touched with the finger, the neighbouring parts quickly and 

 rapidly changed colour, clouds of a bright red colour spread rapidly 

 in every direction over the surface, from the part touched. This dif- 

 fused redness, which was like a blush on the human skin, appeared 

 to be produced by some coloured fluid passing repeatedly to and 

 from minute vesicles on the surface of the skin. The animal swam 

 several times hurriedly across the basin, always with its posterior 

 extremity forward, by repeatedly striking forward the whole of its 

 webbed arms at the same instant. Swimming seemed as unnatural 

 to it, as to a pea-crab, which likewise swims hurriedly backward by 

 striking the water with its tail, or to many bivalve mollusca, which 

 swim backward by flapping their shells. It likewise climbed up 

 the sides of the basin, out of the water, by spreading its arms in 

 every direction, fixing its tender suckers to the sides of the vessel, 

 and carrying the posterior part of its body erect. The granules on 

 the back parts of the adult animal are^about the size of a grain of 

 sand, situate in the true skin, and are seen on the mantle, head, 

 arms and webs. The 0. gramilatus is distinguished by these tuber- 

 cles or granules of the skin, but they are not confined to that spe- 

 cies, and Lamarck suspects that it may be only a variety of the vul- 

 garis. There is still a necessity for minuter observations than we 

 at present possess, for the accurate discrimination of these singular 

 and interesting animals. 



The cartilaginous frame- work of the head is very soft and trans- 

 parent : it forms rather small orbits, very large spherical cavities 

 for the ears, and a small recess between these two shut cavities for 

 lodging the ganglion of the aesophagus, compared to the brain of ver- 

 tebral animals. In place of the osseous or cartilaginous plates extend- 

 iRg down the back of the mantle in the other genera, we find two 

 small cylindrical stiliform cartilages, about the thickness of a crp^v 



