^N/^ 



THE NEW EVOLUTION 



Level representing the adult stage 

 strictly radial ^ / « 



Fig. C. — In fig. B the animal types represented are considered 

 as adults only. The outermost circle has no connection what- 

 ever with the next, nor the next with that within it. There 

 are, however, numerous types connecting the innermost circle 

 with the center. The origin of this condition is illustrated in 

 this diagram. The radially symmetrical coelenterates arise 

 through regular geometrical division from the ovum or egg 

 through the gastrula. Their development is represented by the 

 line from the bottom to the top of the figure, the top being the 

 small central circle in fig. B. The biradiate coelenterates, the 

 ctenophores and the Vermiformes arise through departures from 

 this regular line of geometrical figures which take their origin 

 at or about the early gastrula stage, or perhaps just before it. 



[Z46] 



