TUBE-MAKERS. 321 



puscular nature of the chylaqueous fluid prove it 

 to be subservient to nutrition. 



" The two bloods have two methods of aeration. 

 The ' chylaqueous fluid ' rushes into the lovely 

 tentacles, which in many species wave above the 

 head, and there is aerated, aided by the action 

 of the cilia, which line the inner surface of the 

 tentacles. The ' blood ' is carried to those arbo- 

 rescent tufts without cilia, which branch from 

 each side of the head beneath the tentacles. But, 

 although the respiratory process does undoubtedly 

 take place in these organs, yet in animals so 

 simply constructed, each organ performs more than 

 one function." l 



" The tentacles consist of hollow flattened tubular 

 filaments, furnished with strong muscular walls. 

 Each of these hollow band-like tentacles may be 

 rolled longitudinally, into a cylindrical form, so as 

 to enclose a semicircular space, if they only imper- 

 fectly meet. This inimitable mechanism enables each 

 filament to take up and firmly grasp at any point 

 of its length, a molecule of sand, or if placed in 

 a linear series, a row of molecules. But so per- 

 fect is the disposition, of the muscular fibres, at 



1 See also Dr. T. Williams " On the Mechanism of Aquatic 

 Respiration," in "Annals of Nat. Hist.," ser. ii. vol. xii. (1853), 



P- 395- 



Y 



