NEW INTERPRETATION OF CNIDARIA 339 



The historical circumstances have been the main reason 

 why, since the days \\hen the idea of evolution became 

 accepted for the whole field of biology and above all for the 

 field of phylogenetics— and in connection with this into the 

 fields of systematics and taxonomy— scholars have relied too 

 much on facts that can be observed in ontogenies. The wrong 

 interpretation of the mutual relationship between the ontogeny 

 and the phylogeny ("embryos-ancestors," according to de 

 Beer) has played a particularly fatal role. It can never be 

 repeated frequently enough that a basic mistake was made 

 by the so-called "fundamental biogenetic law" as formulated 

 by Ernst Haeckel which proposed that each ontogeny, even 

 if it was secondarily more or less changed, was in principle 

 a recapitulation of a phylogeny in the sense (which does not 

 appear clearly in the formulation) that these were the earlier 

 adult stages being recapitulated. At the first sight this 

 difference does not appear to be too significant because 

 recapitulations do indeed occur during the ontogenetic devel- 

 opments and they are also highly welcome in our phylogene- 

 tic operations. Even if we do not wish to discuss the whole 

 problem, we will mention one typical example whose 

 consequences have proved fatal. 



This is the phylogenetic evaluation of a characteristic on- 

 togenetic stage which occurs quite frequently, i.e. that of 

 larvae. Any "proof" which could support the idea of evolu- 

 tion was highly welcome during the "storm and stress" 

 period of biology when this idea still had to struggle for its 

 final victory. The planktonic larvae of some sessile or parasitic 

 animal types have not only proved to be of help in endeavours 

 to determine the true nature of the corresponding adult 

 forms which had been considerably changed. Peculiarities that 

 are characteristic of a somewhat broader group of animals 

 are preserved or recapitulated in larvae while at the same time 

 these properties have been lost in their adult forms. Various 

 zoologists, however, have gone further than this by stating 

 that an ancestral form as such is recapitulated in larvae and 



