212 HIGH WATER MARK. 



material, are set around a sort of mouth, and diverge 

 in the form of a bell, or like a campanulate flower. 

 The same wonder-working instrument that we had 

 used before would reveal that these are, in their organ- 

 isation, the very counterpart of the many-folded thread 

 which makes up the gill-leaf of the Mussel. Each of 

 these pellucid filaments is fringed with a double row 

 of cilia, set on the two lateral faces ; and the optical 

 appearance produced by their action is, as before, that 

 of running dark points, which hurry down one side of 

 each filament, and up the opposite. The structure is 

 exactly the same as in the Mussel, save that in the 

 Tubulipora the gill-thread is resolved into a few short 

 threads, which are set in a circular whorl instead of a 

 flat lamina. 



It would be a problem worthy the attention of a 

 skilful mathematician and dynamician, one conversant 

 with the resolution and combination of forces, What 

 ought to be the result of such a complex array of 

 currents ? Twelve rods stand in a funnel-like form, 

 each of which is beset with energetic oars which drive 

 the water rapidly down one side, and up the other : 

 what general motion will be communicated to the 

 water in the vicinity as a whole ? I know not what 

 our Newtons or Laplaces would make of the calcula- 

 tion in their closets, but I know the result that is 

 attained in fact. The general movement is that of a 

 whirlpool : a vortex is produced in the water, the 

 boundary of whose influence is a circle exceeding in 

 diameter by many times that of the bell of filaments. 



