370 THE EVOLUTON OF THE METAZOA 



consist exclusively of the sexually mature and solitary olynthi 

 or ascons. It may be therefore better to speak ot an olynthus 

 stage which appears above all during the ontogeny (perhaps 

 as an already sessile larva or as a kind of a postlarva) of the 

 Calcispongiae. Complex individualities are soon developed 

 by way of a further growth (budding or incomplete divisions) 

 and in these it is frequently difficult to identify the single 

 individuals or persons. A labyrinth of external and internal 

 canals is soon developed. This complex can finally adopt a 

 homogeneous form, it can become an individualized com- 

 plexus (cormus). Most frequently, howxver, we find the 

 olynthus stage not repeated at all. Larvae of benthonic or even 

 sessile animals are not recapitulations of any ancestral forms, 

 neither are spongulae anything of this kind. Their structures 

 and forms show an equally rich variety as can be observed in 

 the Cnidaria larvae. 



The Spongiae have repeatedly been discussed in the present 

 study, in w^hich I have also tried to explain the phylogeny of 

 the Spongiae as it appears to have taken place. I have also criti- 

 cized the opposite arguments, above all those that were 

 brought forward by Tuzet, which try to place the Spongiae 

 as members of the large group of Metazoa. I definitely 

 accept the thesis which considers that the Spongiae evol- 

 ved quite independently of the main body of the actual 

 Metazoa from the cormi of the Choanoflagellata, in spite 

 of the fact that the Spongiae represent a polycellular 

 animal type with a complex structure. Taxonomically the 

 Spongiae must be considered without any doubt as something 

 more than a phylum. We only have to make the decision 

 whether we should place the Spongiae together with other 

 polycellular forms (which evolved in all probability from a 

 common root of protozoan ancestors) into one and the same 

 subregnum of Metazoa, or whether it would be better to 

 consider them as a special megataxon similar to that of a 

 subregnum which could be inserted between the Protozoa and 

 the Metazoa, or the Eumetazoa. In the second case we could 



