168 



AFFINITIES AND GEOGEAPHICAL 



same animal, in an earlier embryotic stage, represents a poly- 

 pidom, it is probable that in the polypiaria is the origin of the 



FIG. 81. 



Ophiura. 



echinodermatous line : it is first the polypidom, then the 

 encrinus, then the free-swimming comatula or feather-star, the 

 last being one of the most graceful animals in existence. In 



FIG. 82. 



Asterias aurantiaca. 



