2. EXTERNAL MORPHOLOGY AND THE GENERAL BODY PLAN 



29 



Fig. 19. The distal ends of tentacles of A - Lamellisabella zachsi; and В - Siboglinum plumosum. 

 (After Ivanov, 1960a.) 



the tip of the lophophore, in other words at the right end of the corkscrew 

 of tentacles. These data, obtained from the study of adults, are fully con- 

 sonant with what is known of the ontogenetic development of the tentacles 

 (Ivanov, 1957b). 



