270 THE EVOLUTION OF THE METAZOA 



has also been accepted by a majority of other zoologists who 

 are not experts in this field. It will be therefore sufficient if we 

 mention that Turbellaria are freely moving animals, and that 

 they feed independently, mostly as predatory animals. There is 

 no reason why we should try to derive them from some sessile 

 or parasitic ancestors. It is therefore very surprising to see how 

 Marcus, an expert in Turbellaria, places the Turbellaria in his 

 sketch of the genealogical tree of the animal world (Marcus, 

 1958:52, Fig. 1) high above the Tentaculata which he locates 

 between the Turbellaria and Cnidaria (Coelenterata = Radiata). 

 Even Chaetognatha appear in this sketch closer to the Coelen- 

 terata than to the Platyhelminthes. At the same time Marcus 

 derives both the Platyhelminthes and Nemertinea from the 

 Sipuncaloidea. One would expect that Marcus considers Tur- 

 bellaria to be a progressive type because they are placed 

 (together with other "-helminthes") by him so high on the 

 genealogical tree. I find it completely incomprehensible 

 when Marcus tries to derive all these lower "worms" from 

 the coelomatic Bilateria (Marcus 1958:33) endeavouring to 

 find in them traces of the coelom cavities while at the same 

 time he makes no difference between an actual coelom (our 

 perigastrocoele) and other coelom cavities, above all the 

 gonocoele. Marcus thus believes the Turbellaria to be second- 

 arily simplified animals which have played a subordinate role 

 only in the phyletic development; he even considers Nemer- 

 tinea to be more primitive than Turbellaria. 



Remane (1957), too, does not stand far from the view pro- 

 posed in Marcus' work. In Remane's sketch of the genealogical 

 tree of the animal world, the Tentaculata can be found placed 

 under the Platyhelminthes whose position is somewhat hesita- 

 tingly indicated. Remane defends himself against Steinbock's 

 accusation that he tries to derive Turbellaria from Annehda; 

 at the same time he states that both these groups had a common 

 ancestral form which as an already segmented animal had neces- 

 sarily been anneloid. It is not important whether complete 

 parapodia and the so-called secondary or somatic segments 



