CNIDARIA AS THE ONLY COELENTERATA 65 



There is one more method which can prove useful in our 

 search to find the relationship connections and herewith 

 the creation of a truly natural animal system. This is my 

 study, the comparison of the so-called parallelisms (they are 

 not identical with analogies!). It has been proved by way of 

 intensive observations that there are certain properties and 

 peculiarities which are easily repeated. We have here, if looked 

 at from the standpoint of genetics, some more or less identical 

 mutations, or complexes of mutations. As an example we can 

 mention the appearance of cnidae. These are complex, not 

 living, but nevertheless organic products of specialized gland 

 cells which are composed of firm (solid) and thickly liquid 

 components. The thickly liquid secretion of cnidocytes is able 

 to liquefy instantly, almost like an explosion with which it can 

 be rightly compared. Here we are particularly interested in the 

 morphological side of this remarkable differentiation in the 

 monocellular glands. 



This organelle, which itself is not alive, can be found in 

 varying stages of evolution in various recent animal groups. 

 The highest level in their progressive evolution can certainly 

 be observed in the cnidae of Cnidaria— and this is why the 

 latter have been given their name. If we make a search "down- 

 wards" we shall find cnida-like formations in various Protista, 

 even in Protophyta, especially those that stand close to Pro- 

 tozoa (Polykrikos and Pouchetia among the Dinoflagellata). It 

 seems that these cnidoids— as I called these cnida-like and yet 

 completely special formations (Hadzi, 1951)— had been deve- 

 loped repeatedly and independently from each other as early 

 as in Protista; later they have evolved in special directions. The 

 foundation, however, the original mutation which had led to 

 their formation seems to have always been the same. Upwards, 

 i.e. above the level which is taken by Cnidaria in the 

 animal system, no real cnidae can any longer be found. The 

 conditions that prevail in Nemertinea have not been completely 

 cleared up. As for Mollusca (Gastropoda) where cnidae have 

 also been found, it is beyond any doubt that in this case we 



