NEW INTERPRETATION OF CNIDARIA 259 



to abandon the first place in the animal system, and thus the 

 starting point of the subsequent progressive evolution; they 

 must yield this place to such unrepresentative worms as the 

 Turbellaria which creep by m.eans of their bellies. The concept 

 which sees in Hydra as well as in all Hydrozoa the most 

 primitive forms of Eumetazoa among all the recent species 

 has been the main obstacle to the reception of our inter- 

 pretation. 



It is quite unimportant what name we give to the supposed 

 turbellarian ancestors of the present Cnidaria; this is even 

 more true since there are still considerable shortcomings in 

 the classification of the recent Turbellaria so that it is constantly 

 necessary to change the classification. It can only be stated 

 with full certainty that the direct ascendants of Cnidaria had 

 already possessed an intestine with an ectodermal gullet and 

 that they had no intestinal diverticula; that instead their intes- 

 tine had developed a tendency to form longitudinal folds. 



The Larvae of Cnidaria 



This may be now the best place to discuss in more detail 

 the formation of larvae in Cnidaria as well as their possible 

 phyletic significance. 



According to a generally valid rule, the larval stage is 

 usually developed in the ontogenies ot benthonic animals, 

 and above all in animal types that live in the sea, as sessile 

 animals. This larval stage lives regularly in plankton. It is 

 therefore a case of a typical and probably also of the oldest 

 and of the most widely accepted deviation that can be observed 

 in the ontogenetic process. The ecologic significance of this 

 stage is clear and it does not need any further discussion, 

 while at the same time there is even now no unanimity among 

 the zoologists regarding the phyletic significance of larvae. 

 During the flowering of comparative embryology (which 

 should be rather called ontogenetics), and under the fresh 



