ON SEA- WEEDS. 157 



the Sea-oak Coralline, and at the same time profusely 

 studded with patches of most beautiful silver lace- 

 work, Fluslra membranacea (another species of zoo- 

 phyte). The movements of the marvellous creatures 

 that occupy these cells, can only be seen and appre- 

 ciated by aid of the microscope, under which instru- 

 ment, says Dr Johnston, " when the polypes are all 

 protruded, they form a beautiful object from their 

 numbers, their delicacy, and the regularity of their 

 disposition, and the vivacity of their motions, now 

 expanding their tentacular into a beautiful campanu- 

 late figure, now contracting the circle, and ever and 

 anon retreating within the shelter of their cells." 

 Dr Landsborough having carefully examined a speci- 

 men, reckoned that on every square inch of the web 

 of the silvery lace, as every cell was inhabited by a 

 living polype, there existed above two millions of in- 

 dustrious, and, doubtless, happy inmates, so that a 

 single colony, on a submarine island, of a foot in 

 length, is almost equal in number to the population 

 of Scotland. 



But a common hand-lens is quite sufficiently power- 

 ful for viewing the singular little mollusc (Spirorbis) 

 that ornaments each frond, making it appear at a 

 short distance as if a number of chalk beads had 

 been newly gummed and sprinkled thereon. 



The shell of this animal is quite flat on one side, 

 and curled like a ram's horn. From the thickest end 

 we see protruded several exquisite feathers and a 

 small stopper, much in the same style as the Sabella. 



