454 THE EVOLUTION OF THE METAZOA 



such the species that stick in the soft sea bottom, e.g. Branchio- 

 cerianthits giganteiis. There also exist, however, other types of 

 life which can be frequently met with and which have not 

 been taken into consideration by Steiner. We can mention here 

 the parasitic way of life (which can hardly be found among the 

 "Deuterostomia"), and the various types of movement and 

 feeding which can be observed in the benthonic animals (from 

 good swimmers such as the Cephalopoda and down to the 

 fully sessile animals that can be found above all among the 

 OHgomeria). 



Steiner takes a correct attitude regarding the relation, 

 ontogeny versus phylogeny. He considers that the ontogenies 

 of the ancestral forms are only recapitulated in the ontogenies 

 of the recent species; yet at the same time we can frequently 

 find in his scheme of the genealogical tree pictures of larvae 

 instead of the pictures of the corresponding imago forms; 

 this gives an impression that the ancestors could be recapitulat- 

 ed in these larvae, as it these larvae could be a kind of repre- 

 sentatives of some ancestral forms. We also get such an 

 impression because Steiner simply transfers some purely 

 ontogenetic processes— such as the morphogeny of the spinal 

 chord by w^ay of a secondarily closed "feeding canal" which 

 finally leads to the formation of the canalis neurentericus and 

 neuroporus— into changes that take place during the adult 

 stage. 



We cannot accept Steiner' s interpretation when he suggests 

 that the enterocoely and the triple metamery evolved as new 

 forms because of the burrowing way of life of the Entero- 

 pneusta. It Steiner had found a correct interpretation, then 

 there could be no homologies in the conditions of the coeloms 

 in the AnneUda and in the Echinodermata (the Protostomia 

 and the Deuterostomia). We must conclude that in spite of 

 all the endeavours made by Steiner to explain rationally these 

 differences, the idea of a branching of the Eumetazoa into the 

 two main lines of the Protostomia and the Deuterostomia still 

 remains highly improbable. 



