PREVIOUS INTERPRETATIONS OF CNIDARIA 77 



intestine (enioderm) of Eumetazoa, and the internal or poste- 

 rior layers of cells into their skin (ectoderm). 



Such is the situation that appears when we try to make a 

 comparison between two items which are, as a matter of fact, 

 incomparable: we are now certain that Parazoa and Eumetazoa, 

 i.e. all the remaining poly cellular animals, cannot have the 

 same origin. It is therefore necessary to separate the Spongiae 

 definitely and for ever from Cnidaria and Ctenophora, and 

 they can not be included among Coelenterata. Even the most 

 recent attempts to try and halt the progress made by Sollas 

 and Delage cannot change this situation. These attempts have 

 been made, as it has already been mentioned, by Tuzet and her 

 collaborators who try to find a justification for this mainly in 

 a supposed discovery of nerve cells in Spongiae, and by 

 Sachwatkin (1956) who tries to overcome the unbridgeable 

 differences that exist in their ontogenies. 



Nobody has foUow^ed the attempt made by K. C. Schneider 

 (1902) who proposed to connect phylogenetically Spongiae and 

 Ctenophora, with a simultaneous exclusion of Cnidaria from 

 this group, which he had called Diskyneta. This has been, to 

 my knowledge, the only attempt w^hich has endeavoured radi- 

 cally to separate the Cnidaria from Ctenophora and in this 

 way to give up the gtoup of Coelenterata; the attempt, how- 

 ever, remained unsuccessful. TiU now the Cnidaria and Cteno- 

 phora have been looked upon as closely connected with each 

 other. The main difference which has been mentioned in this 

 connection has been the presence, or the absence, of cnidae 

 (it has been due to this that the names Cnidaria and Acnidaria 

 have been introduced): yet this difference is not by far of the 

 most decisive importance. Even if Ctenophora quite generally 

 possessed their own genuine cnidae, as this has repeatedly been 

 supposed to be the case in the species Haeckelia (Euchlora) 

 rubra, it would still be necessary to make a clear distinction 

 between Ctenophora and Cnidaria. Cnidae, however, such as 

 they occur in E//r/6/or^,'could actually be of an extraneous origin, 

 as this has already been mentioned above. 



