FORMATION OF TUBE 



289 



replenishment it rises, to display its branchial plume still more 

 vigorously than before, and remains stationary, as if enjoying 

 the freshness of the renovated element, always so grateful the 

 harbinger of health and strength to those whose dwelling is there. 

 The passing spectator would conclude that he now beholds only a 

 beautiful flower, completely expanded, inclining towards the light 

 like some of those ornaments of nature decorating our gardens. 

 He pauses in admiration. But if a drop of liquid mud falls 

 amidst the element from above, disturbing its purity, then, while 

 the plume unfolds to its utmost 

 capacity, does the animal com- 

 mence a slow revolution, the body 

 also passing around within the 

 tube. Now are the thousands of 

 cilia fringing the ribs [i.e. the 

 secondary filaments] of the bran- 

 chiae discovered to be in vigorous 

 activity, and their office to be 

 wondrous. A loose muddy mass 

 is soon afterwards visibly accumu- 

 lating in the bottom of the funnel ; 

 meantime the neck or first seg- 

 ment of the body, rising unusually 

 high above the orifice of the tube, 

 exhibits two trowels beating down 



the thin edjje as they fold and 



/ ,., FIG. 154. Terebella conchilega Pall. 



clasp over the margin, like our upper end of the tube () showing the 

 fingers pressing a flattened cake 

 against the palm of the hand. 

 [This refers to the lappets of 

 the peristomial collar.] During 

 these operations muddy collections are seen descending between 

 the roots of the fans [right and left gills] towards the trowels, 

 while another organ, perhaps the mouth, is also occupied, it 

 may be, in compounding the preparation with adhesive matter. 

 Still does the partial or complete revolution of the plume above, 

 and of the body within the tube, continue ; the bulk of the muddy 

 mass diminishes, activity abates ; it is succeeded by repose, when 

 the tube is found to have received evident prolongation." 



The Terebellids use their numerous tentacles in searching 

 VOL. II TJ 



anterior end of the worm, h, Its head ; 

 t, tentacles collecting sand grains (y) 

 in their grooves ; x, sand grains in 

 mouth of worm ; f, filamentous fringe 

 of tube. (After Watson.) 



