634 



GERARDA STIASNY-WIJNHOFF 



What has been said of Drepanophorus is not true for all 

 Polystilifera. We know species in which mouth and proboscis 

 pore are widely separated and the mouth even lies under the 



Text-fig. G. 

 prob. 



mmt 



rkyadx.w. dn.c. .Kyru^K. 



v.rt.a. oes. 



Schematic longitudinal section of a Monostilif er after B ii r g e r 

 (6, PI. XV, fig. 1, Nemertopsis peronea). 



Text-fig. 7. 



oes 



prob 



Longitudinal section through Prosorochmus after Salensky 

 ("Uber die embryonale Entwicldung des P. viviparus," 

 ' Bull. Acad. Imp. Sciences ', Petersb., 1909, fig. 8). 



brain. But we also know species in which they communicate 

 by one pore ; we even know all the stages between these 

 extremes in the Polystilifera. Brinkmann (4) showed the 

 development of an ectodermal atrium, in which rhynchodaeum 

 and mouth open separately in the Pelagica. He also describes 



