58 



THE EVOLUTION OF THE METAZOA 



Fig. 9. Some cases of transition from bilateral to radial symmetry 

 of entoparasitic "worms" but only on the "head"; A, scolex of 

 Carpohothriiim sp., (after Shipley and Hornell); B, anterior view of 

 the nematode Par^^ro«fWdZSp., (after Baylis);C, cross-section through 

 the scolex of Nematohotbrium sp., (after Fuhrmann); D, cross- 

 section of a polymerian nematode (after Filipjev); E, cross-section 

 of a proglottis oi Anoplacephala sp. (after Becker); F, anterior view 

 of the nematode Oesophagostomum sp., (after Goodey). 



