62 THE EVOLUTION OF THE METAZOA 



The Role of the Polymerization and of the Subsequent 

 Oligomerization During the Phylogeny 



A very important and fruitful criterion for the evaluation 

 of phylogenetic problems has been recently discussed at great 

 length by the well-known Russian scholar, the now unfortu- 

 nately deceased zoologist V. Dogiel. This is the phenomenon 

 of the polymerization of smaller and also of larger morpho- 

 logic units in the body of the animal. The subsequent oli- 

 gomerization is regularly accompanied by differentiation 

 (V. Dogiel, 1954). We must imagine it as a doubling and as 

 a further multiplication of units w^hich takes place in the 

 complex of genes and which is later, during the development 

 of an individual, materialized in the corresponding morpho- 

 logic "parts". By way of this process of polymerization we can 

 explain the development of monoflagellate and mononuclear 

 Flagellata into Poly- and Hypermastigida as well as into the 

 polynuclear species, a development w^hich has finally led also 

 to the formation of Ciliata. Various ciliary organelles of a 

 complex nature have evolved by w^ay of a specialization of cilia 

 from this polymerization; the polymerized nuclei have become 

 differentiated into macro and micronuclei by way of oUgomeri- 

 zation. The ribs of Ctenophora have been developed by w^ay 

 of oligomerization and differentiation. The single pair of 

 tentacles as it occurs in Turbellaria has developed into circlets 

 which frequently consist of multiplied tentacles as in the 

 Cnidaria. A subsequent oligomerization led in some cases 

 observed in Hydrozoa, to a reduction of tentacles to the 

 number of two, or even to their complete disappearance. 

 The polymerization followed by oligomerization and differen- 

 tiation finally led to the formation of various forms of ten- 

 tacles in one and the same individual (e.g. in polyps of 

 Eleutheria and of medusae see Fig. 11 and 12). 



Naturally, we must be careful to differentiate, when we take 

 into consideration this regularity, between a primary simpli- 

 city and a secondary simplicity which has developed by way 



