362 



THE EVOLUTION OF THE METAZOA 



These Flagellata had afterwards evolvedalongat least four di- 

 verging lines: The first two lines ended "blindly" as Protozoa. 

 The first of these lines is represented by the Flagellata. In this 

 line we can observe a strong inclination to polymerization. 

 The line ends with the Hypermastigina which now only live 

 in other animals. The second line is very short, it consists of a 



Metazoa 

 / EumetSzoa \ 



Zoonagellata 



TurbeUaria / 



Metazoa 

 /Parazoa ^ 



Parasitic 

 FlageUata 



FLAGELLATA 

 (Protozoa) 



Fig. 49. Evolutionary relationship Flagellata-Metazoa; (orig). 



few species only w^hich belong to the Opalinidae (Opalinata, 

 according to Wessenberg). These again live as parasites in the 

 bodies of other animals. The third line had actually broken 

 from the narrow frame work of the Protozoa, yet it evolved 

 into a weak branch only of "polycellular" forms or Metazoa, 

 i.e. into the Spongiae whose subsequent development had 

 soon ended blindly (Fig. 49). It was the fourth line which 

 had played a leading role; it had begun with the primitive 

 Ciliata and it had continued to evolve all the way along the 

 main line of the development of the Eumetazoa. 



