THE SHORES OF BRITAIN. 638 
lows in miniature. Beyond its beauty I know 
not that this little creature has any obvious claim 
to our consideration, except that, in common with 
other sea-plants, it gives out oxygen, and thus 
maintains the element in which it grows in a state 
fit for the support of animal life. But this is a 
service vastly important, and explains why the 
“floor of the ocean” is covered, as it appears to 
be, with such a profusion of vegetable life. And 
here so wisely is the balance kept up between the. 
animals which absorb oxygen and the plants which 
evolve it, that, perhaps, the world could not afford 
to lose a single species of either without derange- 
ment of the existing order, which would be fol- 
lowed by manifest inconvenience. Of course our 
little Coralline cannot do much to promote this 
object; but that it does exert some beneficial in- 
fluence, we have evidence in an experiment of 
Dr. Johnston, whose researches on these neglected 
tribes are so interesting. ‘Was there a need,” he 
observes, “of adding any additional proof of the 
vegetability of the Corallines, an experiment in pro- 
gress before me would seem to supply it. It is 
now eight weeks ago since I placed in a small 
glass jar, containing about six ounces of pure sea- 
water, a tuft of the living Corallina officinalis, to 
which were attached two or three minute Con/erve, 
and the very young frond of a green Ulva, while 
numerous Rissow, several little Mussels, and An- 
nelides, and a Star-fish, were crawling amid the 
branches. The jar was placed on a table, and was 
seldom disturbed, though occasionally looked at; 
