CHAPTER 1 



CNIDARIA AS THE ONLY 

 COELENTERATA 



The Systematic Position of the Spongiae 



The next step, apparently without connection with the former, 

 was made when some well-known researchers especially Sollas 

 and Delage, came to the conclusion that the Spongiae must 

 not only be placed far from the immediate vicinity of Cnidaria, 

 but also that they must be completely separated from the Coe- 

 lenterata and even from all the remaining real Metazoa, the 

 Eumetazoa; they must appear completely isolated as an 

 independent type, as Parazoa or Enantiozoa. We must 

 consider this separation as being definite, and, in my 

 opinion, nothing can be changed in this respects by recent 

 attempts made particularly by Miss O. Tuzet and her col- 

 laborators. 



On the basis of works of older irvestigators, especially 

 the researchers into the ontogeny of Spongiae (Metschnikoff, 

 Delage, etc.) it is no longer necessary to defer d the special 

 position that the Spongiae have as Parazoa (Sollas) in the 

 animal classification. Recently, however, a tendency has arisen 

 which aims at a revision of this point of view and tries 

 to bring Spongiae back amongst the other Metazoa. The 

 French school in particular, which created the term Enantio- 

 zoa (Delage), attempts to cancel out the progress that 

 has been achieved; Tuzet points in this connection mainly 

 to the following evidence: (1) According to her School, 

 the Spongiae have a nervous system; (2) the choanocytes 

 are found in the other Metazoa; (3) the stretching out and 

 the pulling in of a part of the blastoderm observed in the 



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