NEW INTERPRETATION OF CNIDARIA 341 



very careful. Yet we should be even more careful when in 

 this search we w4sh to identify the embryonic, post-embryonic, 

 and above all the larval stages. Everything shows that the 

 peculiarities of the not fully adult phases are even more subject 

 to greater and special changes, regardless of the fact whether 

 they live under the protection of the maternal animal or of 

 protective hulls, or finally as free animals that feed independ- 

 ently; these phases can therefore not be considered as re- 

 capitulations in the old sense of the word. The changes and 

 new formations which have a purely ontogenetic character 

 have nothing in common with the peculiarities of the adult 

 animal. It is therefore wrong to endeavour to show that 

 such characteristics had already functioned in the ancestors 

 of recent forms. This can be best seen in the attempt made 

 by Boettger (1952) who tried to explain functionally the 

 changes of the oral and anal orifices that can be observed in 

 the ontogenies of the Eumetazoa (Protostomia-Deutero- 

 stomia). These and other similar changes can take place during 

 the ontogenetic ontogenies only, thus during the non- 

 functioning phase of the evolution. 



This shows that generally we must be very cautious when 

 we try to use the ontogenetic facts for our phylogenetic 

 constructions (speculations). Other facts and methods must be 

 also constantly taken into consideration. We must constantly 

 distinguish between the material established in the non- 

 functioning phases and that established in the functioning 

 phases yet not in the sense of the adult stage, and between the 

 final stages of development and those stages which directly pre- 

 cede the definitive stage, e.g. metamorphosis and the stage which 

 frequently follows it. Metamorphosis emerged as a necessary 

 phase of the ontogenies ; it is a consequence of a widely dif- 

 ferent development of the larval phase. Such a metamorphosis 

 can have really catastrophic proportions, or in other cases 

 it can be considered as a non-functional ontogenetic event. 



Those authors who try, too quickly, to conclude, on the basis 

 of some similarities that can be observed during the larval 

 23 



