27 8 



SEA FABLES EXPLAINED. 



hydro-dynamic law which governs its mode of self-propulsion 

 when swimming, and possibly in some degree within the 

 control of the animal the latter is relieved of much of the 

 weight of its shell. When the Nautilus is at the bottom of 

 the sea its movement is like that of a snail crawling along 



FIG. 34. THE PEARLY NAUTILUS (Nautilus pompilius)> AND SECTION OF 



ITS SHELL. After Professor Owen. 



a a, Partitions ; b b, chambers ; b\ the last-formed chamber, in which the 

 animal lives ; c c, the siphuncle ; d, attaching muscle ; e e, the hollow 

 arms ; ff y retractile tentacles ; , muscular disk, or foot ; h, the eye j i, 

 position of funnel. 



upon the ground with its shell above it. The shell, in 

 proportion to the size of the animal that inhabits it, is a 

 heavy one, and unless it were rendered semi-buoyant, its 

 owner's strength would be severely taxed by the effort to 

 drag it along. By the means indicated this portable 



