96 THE EVOLUTION OF THE METAZOA 



Goette, to prove the close relationship between Scyphozoa 

 and Anthozoa and to unite them into one class. The main 

 reason for these attempts has been the supposed presence 

 of an ectodermal pharynx both in Scyphozoa as well as in 

 Anthozoa. There can be no doubt that an ectodermal gullet 

 does really occur in Anthozoa. On the other hand, I succeeded 

 in showing several years ago (Hadzi, 1911), that the Scyphozoa 

 do not possess an ectodermal gullet. It has even been found 

 that the opposite is really true, i.e. the oral area of the scypho- 

 polyp has been raised to an oral cone so that the limit between 

 the ectoderm and the entoderm runs along the oral margin. 

 Even if the taeniolae of scyphopolyps represent the 

 remains of the sarcosepta that can be found in Anthozoa, 

 they have nevertheless been developed in their own direction. 

 In this way the division of the t^'O subgroups of Cnidaria 

 into tv\'o independent classes seems to be fully justified. 



If we disregard the form of medusa and if we take into 

 consideration the polyp form only, it could seem at first 

 sight to be justified to see in the sequence Hydrozoa — Scypho- 

 zoa — Anthozoa a progressive line of development. This would 

 fully correspond to the principle of evolution of a generally 

 progressive development. It is therefore understandable that 

 this sequence has generally and incontestably been regarded 

 as the sequence which agrees with the line that evolution 

 had taken; we can say that it has been accepted as a postulate 

 which nobody has even tried to touch or doubt. 



To this should be added the fact that in connection with 

 Hydrozoa, and with the solitarily living Hydra,— hec2Lust 

 of the recapitulation theory— we have an example of a metazo- 

 an that embodies an ideal transition from Flagellata among 

 Protozoa to Metazoa and the ideal pattern of a gastraea 

 composed of two body layers. The difference between Hydra 

 and gastraea consists in its circlet of tentacles and in its life 

 on the bottom only. It was easy to derive first the scyphopolyp 

 and later the anthopolyp form Hjdra as the primitive form 

 of aU Hydrozoa. Everything seemed to agree well. Nothing 



