NEW INTERPRETATION OF CNIDARIA 309 



emphasized that a formation of syncytia can also be observed 

 in Spongiae, and not only in plants. 



The embryonic development, the ontogeny, emerged as a 

 necessary consequence of this state in all these lines of evolu- 

 tion, thus in Volvocidae and in various other polycellular 

 algae, in Cormophyta, and finally also in Spongiae. It is there- 

 fore not surprising to see that there is a great difference bet- 

 ween these ontogenies as a result of their separate Unes of 

 evolution; this is also true for Spongiae in comparison with 

 the Eumetazoa. No other higher animal group has ever evolved 

 from Spongiae. The further evolution of the animalic bionts 

 had begun from another centre. 



The most successful attack against the limiting influence 

 of the monocellular state, an attack which has finally led to 

 the formation of the most highly organized beings, of the 

 polycellular animals and man, was made by way of poly- 

 merization, the pluraUty of nuclei in a cytoplasmatic or plas- 

 modial body which preserves its individuaHty, and by way 

 of a subsequent cellularization (Fig. 48). The way along 

 which this development had taken place and how it occurred 

 has already been partly discussed, but we will still return to 

 this problem. The importance and the significance of the 

 difference which exists between the development of multiple 

 cells by way of a formation of colonies or cormi, and the 

 developm.ent of such cells by way of polymerization can 

 easily be understood. The first type of development is charac- 

 teristic of plants, and the second of animals. The two types 

 of development have in common (1) the growth in size; (2) 

 the possibility of a differentiation; and (3) the sexual phase 

 with the ontogeny at its end. Cellularity can also be 

 considered as one of these common properties even if here 

 there is one important difference. In the polycellular plants 

 the cellularity is a primary element which is obstinately preserv- 

 ed; in the Eumetazoa on the other hand cellularity is a 

 secondary development from a polykaryonic state. Cel- 

 lularity is almost never completely carried through in the 

 21 



