104 THE INVERTEBRATE PHYLA 



Tunicata Arthropoda 



Acrania / Chaetognatha Echinodermala 

 Vertebrata 



Enteropneusta 



Mollusca 



Annelida 



(Chordonia) ^omalo- ( Ambulocralia) 

 pterygia) 



Spongiaria 



Molluscoidea 



(Deuterostomia) 



Ctenophora 



(Coelenterata) 

 Metazoa 



Rhizopoda 



Sporozoa 



Ciliata 

 (Cytoidea) 



Flagellata 

 (Cytomorpha) 



Protozoa 

 Fig. 36. Grobben's classification of the Invertebrate Phyla. 



specialisations of parts of one original opening which is repre- 

 sented in most embryos by the blastopore. 



" When, however, we come to apply this doctrine to the Chordata 

 we stand on more debatable ground. Placing the Enteropneusta 

 on one side as not obviously conforming to our plan, we find that 

 it is a fact of observation that in the Chordata the blastopore 



