MAMMALIA AYES 



REPTILIA 



^ z 



INSECTA 



AMPHIBIA 



PISCES 



VERTEBPATA 



MrRIAPODA 



CEPHALOCHOPDATA 



UPOCHOPDA 

 HEMICHOPOATA 



ONYCOPHOPA 



APACHNIDA 



CRUSTACEA 



/ 



CHORD ATA 



ARTHROPODA 



ECHINODERMA 



NEMA THEL MIN THES 



MOLLUSC A 



CTENOPHORA 



COELENTERATA 



PORIFERA 



PROTOZOA 



PRIMITIVE PLANT-ANIMAL 



Fig. 75. — Scheme representing a possible relation of the various animal groups. 

 The phyla are given in large, and the classes in small, type. When read from the 

 bottom of the figure the diagram is useful in that it represents accurately a series 

 of ascending levels of animal complexity. Some authorities consider the Chordata 

 to have originated by way of the Annelida; others regard the Arthropoda as the 

 source of the Chordata. Still other interpretations are possible. (After Allee, slighdy 

 modified.) 



