636 



THE POPULAR SCIENCE MONTHLY. 



by naturalists as equal units, formed of the same parts, having each a 

 real individuality. The name Somites, which has been given them, 

 shows the tendency to consider them as true elementary animals as- 

 sociated in colonies (Figs. 13 and 14). The power possessed by the 

 segments of certain worms to individualize themselves and form new 

 colonies is strong evidence in favor of this view. Polymorphism and 

 the concentration of parts explain how a Peripatus or a Myriapod can 



Fig. 14,— Lobsteb with the Somiteb separated fbom each other, the Appendages being 

 ALL REMOVED EXCEPT THE TERMINAL SwiMMEKETS. cu, carapacc ; t, teleon ; 2, third abdom- 

 inal somite with its appendages. 



become a spider or an insect, how different Crustacea arise from a 

 common stem, how from another form of colony have arisen all the 

 Annelida. It has been often said that Echinoderms, Star-fishes, Ophiu- 

 rans, were only colonies united by the head (Fig. 15). They are, at 

 least, all colonies, but of a special nature. 



Can we say as much of the Mollusca and Vertebrata, all the parts 

 of which are so closely united, and which are the giants of creation ? 

 Are there simple forms of association which can explain the marvelous 

 organization of these superior types of creation — as we have explained 

 the Siphoniferae, Coral Polyps, Echinoderms, and Arthropoda ? 



