86 



PART I. GENERAL ACCOUNT 



Being sedentary animals pogonophores can possess only a passive type of 

 feeding adapted to filtration or collecting plankton and detritus. The ciliated 

 bands along the sides of the tentacles suck water from the tip of the crown of 

 tentacles down into the intertentacular cavity and thence out between the 

 bases of the ventral tentacles, where there is always an aperture of some kind 

 even in those species where the tentacles are joined together. It is possible 

 that the microscopic organisms and particles of detritus floating in the water 

 are trapped in the dense network of pinnules which, in this way, play the 

 role of filter. 



The possibility of phagocytic digestion by cells of the tentacles may be 



Fig. 59. Transverse section through tentacular crown of Spirobrachia grandis. 

 cav - intertentacular cavity; cil - ciliated band; сое - coelomic canal of tentacle; nt - tentacular 

 nerve; pi - pinnule; tdl - left dorsal tentacle; te - outermost marginal tentacle; ti- innermost 

 marginal tentacle; va - afferent vessel; ve - efferent vessel. (After Ivanov, 1960a.) 



excluded because of the strong development of the cuticle. The characteristic 

 picture of intracellular digestion, usually so easily demonstrable in sections, 

 has been seen in neither the tentacles nor the pinnules. There thus remains 

 only the absorption of dissolved food substances. 



Digestive enzymes probably act in the intertentacular cavity, secreted by 

 the epidermis of the tentacles or perhaps by special gland cells which may 

 sometimes be seen at the base of the pinnules. Digestion of the food possibly 

 takes place in this same cavity. The dissolved food substances are then ab- 

 sorbed by the pinnules which play the role of a sort intestinal layer of villi 

 and take these materials into the blood in their intracellular capillaries. 



