88 



STUDIES IN LIFE AND SENSE. 



The margins of the foot, in this view of matters, have been pro- 

 longed in the young cuttlefish to form eight, ten, or more arms, and 

 the front and sides of the foot, having overgrown the mouth, are 

 united in front, so that the mouth appears to be placed in the centre 

 of the foot, instead of in front and above it, as in other molluscs. 

 So, also, most naturalists maintain, and with every appearance of 

 correctness, that the characteristic " funnel ;; of the cuttlefishes to 

 be hereafter referred to is an organ formed by two side processes 

 of the foot, named epipodia. Adopting the view thus sanctioned by 

 competent authority, we may trace in a cuttlefish the highly modified 

 form of a snail or whelk, and the still more modified form of the 

 mussel tribes. The foot, instead of growing backwards and down- 

 wards as in the snail, and thus forming a broad walking disc, comes 

 to grow over the mouth in front. So that, placing a cuttlefish in 

 structural comparison with a whelk or mussel, we should have to set 

 it head downwards, when the foot (or arms) would be lowest, and 

 the great bulk of the body, with the heart uppermost, would be 

 situated, as in the snail, above the foot. 



The group of the cuttlefishes may be said to divide itself in the 

 most natural fashion into two main divisions. The first of these 



groups includes all 

 living cuttlefishes save 

 one the pearly nau- 

 tilus. This first divi- 

 sion is that of the 

 DibranckiateS) or two- 

 gilled cuttlefishes. The 

 familiar octopus (fig. 

 5), the loligos or 

 squids, the sepias, and 

 the argonauts or paper 

 nautili, are amongst 

 the best known of its 

 representatives. The 

 second group is repre- 

 sented by a single 

 living cuttlefish, the 

 pearly nautilus (Nau- 

 tilus Pompilius), just 

 mentioned, and by 

 many fossil and extinct forms. These are the Tetrabranchiates^ 

 or four-gilled cephalopods, which, in respect of their general 

 anatomy, their development in time, and their distribution in space, 

 may be said to stand apart in the most marked fashion from the 

 two-gilled cuttles which throng the seas of to-day. We shall dis- 



Fic. 5. CUTTLEFISH SWIMMING. 



