1832.] HABITS OF THE CUTTLE-FISH. 5 



surface of the stream, it is converted into groups of beautifully radiated 

 tibres resembling arragonite. The beds of lava rise in successive 

 gently-sloping plains, towards the interior, whence the deluges of melted 

 stone have originally proceeded. Within historical times, no signs 

 of volcanic activity have, I believe, been manifested in any part of 

 St. Jago. Even the form of a crater can but rarely be discovered on 

 the summits of the many red cindery hills ; yet the more recent 

 streams can be distinguished on the coast, forming lines of cliffs of less 

 height, but stretching out in advance of those belonging to an older 

 series: the height of the cliffs thus affording a rude measure of the 

 age of the streams. 



During our stay, I observed the habits of some marine animals. A 

 large Aplysia is very common. This sea-slug is about five inches long ; 

 and is of a dirty yellowish colour, veined with purple. On each side 

 of the lower surface, or foot, there is a broad membrane, which appears 

 sometimes to act as a ventilator, in causing a current of water to flow 

 over the dorsal branchiae or lungs. It feeds on the delicate sea-weeds 

 which grow among the stones in muddy and shallow water; and I 

 found in its stomach several small pebbles, as in the gizzard of a bird. 

 This slug when disturbed, emits a very fine purplish-red fluid, which 

 stains the water for the space of a foot around. Besides this means 

 of defence, an acrid secretion, which is spread over its body, causes 

 a sharp, stinging sensation, similar to that produced by the Physalia, 

 or Portuguese man-of-war. 



I was much interested, on several occasions, by watching the habits 

 of an Octopus, or cuttle-fish. Although' common in the pools of water 

 left by the retiring tide, these animals were not easily caught By 

 means of their long arms and suckers, they could drag their bodies into 

 very narrow crevices ; and when thus fixed, it required great force to 

 remove them. At other times they darted tail first, \viththerapidity 

 of an arrow, from one side of the pool to the other, at the same instant 

 discolouring the water with a dark chestnut-brown ink. These animals 

 also escape detection by a very extraordinary, chameleon-like power of 

 changing their colour. They appear to vary their tints according to the 

 nature of the ground over which they pass : when in deep water, their 

 general shade was brownish-purple, but when placed on the land, or 

 in shallow water, this dark tint changed into one of a yeUowish-green. 

 The colour, examined more carefully, was a French grey, with numerous 

 minute spots of bright yellow : the former of these varied in intensity ; 

 the latter entirely disappeared and appeared again by turns. These 

 changes were effected in such a manner, that clouds, varying in tint 

 between a hyacinth-red and a chestnut-brown,* were continually passing 

 over the body. Any part, being subjected to a slight shock of galvanism, 

 became almost black : a similar effect, but in a less degree, was pro- 

 duced by scratching the skin with a needle. These clouds, or blushes 

 as they may be called, are said to be produced by the alternate expansion 

 and contraction of minute vesicles containing variously coloured fluids.! 



* So named according to Patrick Symes's nomenclature. 



J See "Encyclop. of Anat. and Physiol.," article Cephalopoda, 



