442 THE EVOLUTION OF THE METAZOA 



under the application of our working method; I will therefore 

 exclude from this account all those elements which could be 

 too hypothetical. 



The situation has become slightly better now because there 

 is hardly any living zoologist who would still be willing to 

 accept a suggestion to derive the Chordoma either from the 

 Nemertinea (Hubrecht, 1883), or from the Arthropoda of the 

 type of the Umuliis (Gaskell, 1895-1910, and Patten, 1912). 

 The interpretation which derives the Chordoma directly 

 from the Annelida (Dohrn, 1875; Semper, 1875-6; Minot, 

 1897; Delsman, 1922; and many others) finds recently less 

 and less acceptance, though earlier it was frequently put for- 

 ward; the interpretation itself was actually based on a fantastic 

 idea that had been proposed by Hilaire (1818). The same 

 interpretation (it is in reality only a minor hypothesis) has 

 recently been revived in a somewhat changed form, w^hen 

 the Oligomeria have been suggested as a possible starting 

 point of the evolution of the Chordoma. The Oligomeria 

 themselves, however, can easily be derived, as we have 

 already shown, from the polymerous Annelida. Yet even 

 within the limits of a general theory which derives the 

 Chordoma from the Oligomeria there exist several possibilities 

 which can claim various degrees of probability. There exist 

 therefore several interpretations of this kind which were sug- 

 gested, e.g. by Bateson (1884-6), Brooks (1893), WiUey (1894), 

 and Garstang (189^8) whose interpretation has been accepted 

 by Sir Gavin de Beer and recently by N. J. Berrill (1955) in 

 a special book he wrote on this subject. 



I do not intend to begin here with a detailed analysis 

 of these hypotheses about the supposed annelidan-arthro- 

 podan ancestors of the Chordoma; we will agree on 

 this point with the critical discussion written by Berrill 

 (Berrill, 1955:2-5). I wish only to state that the peculiarities 

 which the Chordoma have in common with the Annelida 

 (for example the solenocytes, the close connection between 

 the sexual organs and the nephridia). These peculiarities have 



