82 THE EVOLUTION OF THE METAZOA 



supplement to the fifth volume of her book The Invertebrates 

 where my hypothesis can also be found mentioned under the 

 title "Retrospect" (p. 730). She refuses straightforwardly to 

 accept my hypothesis which she calls "the fantastic theory of 

 Hadzi," and adds, "Hadzi gives no real grounds for this view, 

 only theoretical vaporizing." This opinion, or rather judgment, 

 is not only unjust, it is also wrong. The way I proceeded to 

 found my hypothesis has been exactly the same as has been 

 done by other zoologists, Hyman included. I referred to well- 

 established facts which I tried to bring into a new focus and to 

 give them new interpretations. In this connection Hyman has 

 omitted to mention that in the meantime, P. Us (1932), one of 

 my students, succeeded in proving the older data about the 

 development of the mesoderm in Ctenophora as it had been 

 published by Metschnikoff to be essentially correct (Fig. 

 15). One w^ould expect in an objective criticism, to be able 

 to find at least some arguments quoted and an honest statement 

 that there have been zoologists who have considered my hypo- 

 thesis to be feasable,at least before the author begins a straight- 

 forward refusal of my thesis. In this connection Hyman could 

 have remembered what she read in the article "Evolution of 

 Metazoa" by Sir Gavin de Beer (in the book ^'E^volution as a 

 Process,"'' 1954). In it a paragraph from the book by MacBride is 

 quoted which refers to Lang, and which states that the ciUary 

 seams of the eight lobes that occur in Mliller's larva are 

 "jointed edgewise so as to form combs." Anyhow, on the basis 

 of the numerous similarities that exist between Ctenophora 

 and Polycladida, MacBride, according to de Beer, comes to 

 the conclusion "that Miiller's larva represents a pelagic Cteno- 

 phore — like adult ancestor of Polyclada, and that the Platy- 

 helminthes were evolved from the Ctenophora." De Beer 

 accepts my hypothesis because he obviously thinks it to be 

 better founded and more probable than other previous hypo- 

 theses. In the introduction to the present study it has been 

 mentioned that in our research in the phylogenetic problems 

 no progress can be made without some imagination, or rather 



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