372 THE EVOLUTION OF THE METAZOA 



food to the animal. In spite of this we still prefer the name 

 Parazoa because the word itself ends in -^oa; such an ending is 

 much more suitable for the few subregna of the animal world 

 and it should therefore be used in this sense only. 



The 'Eiimeta^oa and Their Subdivisions 



The Elimination of the terms Coelenterata : Coelomata. So far 

 there have been no essential differences between our system 

 of the animal world and the traditional and generally used 

 systems. Yet the whole basis of the subsequent system neces- 

 sarily becomes changed when we take into consideration the 

 consequences of our interpretation that the real polycellular 

 forms (the Eumetazoa, or the Metazoa s. str.) had evolved from 

 the polynuclear (i.e. polykaryonic) or plasmodial Protociliata. 

 From now on the organization does not develop anew from 

 some independent units, from the protistic individuals which 

 had been previously free, as had been the case with the 

 "Metaphyta" and with the Spongiae. This kind of evolution 

 leads, with a few "initial" exceptions (Volvocales), exclusively 

 to the formation of sessile organisms. The evolution which had 

 led to higher forms followed another principle: and in these the 

 cells gathered to form a new individuality of a higher type, a 

 new whole with a complex structure. 



From the very beginning the genuine animal freely-living 

 polycellular forms had taken over the higher organization 

 which had been reached already on the level of the Protozoa 

 (Ciliata). Thus, it was the eumetazoan organism which formed 

 these cells and not conversely that the previously individual 

 cells formed a polycellular organism, as was the case wdth the 

 Metaphyta and with the Spongiae. This is the only way the 

 development of an internal digestive organ can be rationally 

 explained: thus neither by way of an invagination of a hollow 

 sphere, nor by a wandering in of individual earlier skin cells 

 into the interior of the same sphere. The names Enterozoa, 

 according to Lankester, or Gastrobionta (animals with an 



