NEW INTERPRETATION OF CNIDARIA 307 



agrees with their type of feeding. Even androgametes which 

 preserved their free mobiHty are now only active when 

 they are transferred from place to place. This situation has 

 finally become even more complicated because of an intro- 

 duction of a remarkable alternation of generations. 



In spite of a strong inclination of the plant cells to remain 

 mutually separated they have nevertheless developed plasmatic 

 connections which go through the cell walls, or they 

 had even completely relinquished their cell walls and 

 had developed in this way syncytia. The case of Caulerpa 

 and of the whole group it belongs to is w^ell enough 

 know^n. Here a total polykaryonic stage had been reached. 

 Among the higher plants it is not seldom that partial syncytia 

 can be found. 



The animals certainly pursued several lines in their evolu- 

 tion, yet it was one line only which succeeded in making 

 essential progress while all the remaining lines had already 

 come to a stop at the level of Protozoa. Another primitive 

 line led to the formation of Spongiae. The evolution of animals 

 has been much more vivid because of their heterotrophic type 

 of feeding, because of their free mobiHty w^hich is connected 

 with the type of feeding, and— w^hich is a very important 

 fact — because of the very thin walls of their cells. The limita- 

 tions of the monocellular and mononuclear state were over- 

 come along at least three paths. One of these was, so it seems,, 

 a development which led to a slight increase of the cyto- 

 plasmatic mass which was subsequently divided half-way, first 

 into two and later into several parts; its result had been the 

 formation of considerably larger complex individuals. Yet this 

 division into halves has not led to differentiation, it remained 

 rather mechanical, and its result has only been an increased 

 breathing surface. It was soon combined with a polymerization 

 of the nucleus. This is how the comparatively large For- 

 aminifera, e.g. of the type of Nummnlites, evolved. Yet 

 no genuine Metazoa had ever possibly developed along this 

 way. 



