THE PAST AND PRESENT OF THE CUTTLEFISHES. 89 



cover that the clues to the evolution of the cuttlefish race emerge in 

 greater part from the fossil history of the four-gilled forms. But as 

 the two-gilled members of the group constitute well-nigh its whole 

 living population, the general nature of these animals may be most 

 satisfactorily investigated if, in the first instance, we deal with the 

 common representatives of the class. Thereafter we may profitably 

 attempt the consideration of the pearly nautilus and the general re- 

 latives of the cephalopods in time past and in the geological aeons 

 wherein lies the childhood as well as the past perfection of the 

 race. 



Amongst the ordinary or two-gilled cuttlefishes, various diver- 

 sities of external form are readily discernible. The elongated body 

 of the squids, or Tetithida a group first defined by Aristotle himself 

 terminated by its arrow-shaped fin, presents us with a characteristic 

 cuttlefish form. The sepias, in which the body is of rounded form 

 and bordered by a soft fin, constitute a second familiar type, and the 

 octopi, in which the body is of globular shape and of which the arms 

 are connected by intervening webs for a considerable portion of their 

 extent, represent a third illustration of the variety of external con- 

 figuration in these animals. But under the relatively slight variations 

 in form exhibited by the cuttlefishes, there exists a general agreement 

 in bodily structure which renders their examination a tolerably easy 

 matter. The body in all, for example, is enclosed in a muscular 

 mantle-sac the " mantle " being the name given to the general 

 investing skin or integument of the molluscs at large. It is this 

 " mantle," or " pallium," as it is technically named, which forms the 

 " shell," wherever that structure is found, and under whatever guise 

 it is represented. When we regard an octopus or squid, we are 

 looking at the outer surface of the " mantle," which thus, by its dis- 

 position and arrangement, practically forms the body of these 

 animals. Where an external and true shell exists in cuttlefishes, 

 we shall find that this structure simply represents the outer pro- 

 tection of- the mantle or integument which has secreted and pro- 

 duced it. 



One of the most remarkable traits of cuttlefish existence is the 

 curious play of " shot " colours which takes place in their integument 

 I have seen a loligo, or squid, stranded on the sea-beach make 

 glorious its dying agonies by a play of colours of the most astound- 

 ing description. The natural purplish tint of the body was now and 

 again deepened to well-nigh a dark blue ; the slightest touch served 

 to develop a patch of angry pink ; and continually over the whole 

 surface of the body the hues and tints, ranging from dark purple to 

 light red, succeeded each other in rapid array. This chameleon-like 

 property of the skin of the cuttlefishes was familiar to the classical 

 poets and naturalists. Oppian speaks of the cuttles, when 



