644 GERARDA STIASNY-WIJNHOFF 



Pelagica no traces of a reduction in the proboscidian system 

 are to be found, as emphatically stated by Brinkmann, 

 we must consider this tribe as the more primitive one in the 

 Polystilifera. 



The structure of the muscular wall of the rhyncho- 

 coelomic cavity seems to prove this. In 1914 I tried to demon- 

 strate (18) that the proboscis and its sheath together are an 

 invagination of the body-wall, and that all parts of the body- 



Text-fig. 16. 



Section through the proboscis of Amphiporus pulcher after 

 Biirger (6, PI. xxiii, fig. 3). 



wall are to be found in situ, either in the proboscis or in 

 the wall of the sheath. In the Anopla this seems quite clear, 

 but in the Enopla several difficulties arise. The presence of 

 the third or inner muscular layer of the body-wall, which in 

 Palaeonemerteans is characteristic, the iimer circular muscle- 

 coat (Text-fig. 1, a), has never been demonstrated, though in 

 Drepanophorus, as I know now, its presence is quite clear 

 in the stomodaeal region. iVlso the dorsoventral muscles show 

 the same peculiarities as in the Anopla, where they are derivates 

 of this musculature. So it was not certain whether we had 

 a right to look for this layer in the proboscidian system of the 



diviae (Burger) belong to the Monostilifera. Through this conclusion 

 we have excluded Drepanophorus valdiviae from the Polystilifera, 

 in which it might cause much trouble by the different structure of ahuost 

 every organ. 



