m 



THE NEW EVOLUTION 





::^: 



I 



o 



Fig. D. — ^The animarsymmetries. i. — The"symmetry of the 

 germ cells, which is also the fundamental symmetry of the proto- 

 zoans; the dotted lines are assumed to radiate from the center of 

 a sphere, x. — Coelenterate radial symmetry, viewed along the 

 axis through the mouth and the opposite pole. 3. — Biradiate 

 symmetry, a modification of the preceding (2.), found in coelen- 

 terates only. 4. — ^The cross symmetry of i he ctenophores. 5. — 

 The partly bilateral and partly radial symmetry of a tapeworm in 

 which the head or scolex is four sided. 6. — Bilateral symmetry, 

 with a single axis. 7. — ^The pseudoradial symmetry of an echino- 

 derm — really bilateral symmetry with the axis curved in a circle, 

 half of the five segments of the body failing to develop in the 

 adult. 



[150] 



