OUR SEA-ANEMONES. 255 




















myriads of minute vibrating lashes, or cilia, that cover all 
parts of the interior surface, and this same surface of soft 
membrane has the power of absorbing such nutritious sub- 
stances as each organ may require, from the fluid that bathes 
it, and also the oxygen contained in the sea-water. Indeed 
it is probable that every part of the surface, both external 
and internal, has the power of absorbing oxygen; but it is , 
reasonable to conclude, that this takes place most rapidly in 
the tentacles and internal membranes where the structure is 
most delicate. 
We usually notice, when trying to remove one of these 
Actinias from its rock, a large number of white, thread-like 
organs, emerging both from the mouth and from minute 
openings through the sides of the body. These organs 
= {ppear to be for the defence of the creature, since they are 
-found to -be composed almost entirely of minute poison- 
darts, or lasso-cells, arranged side by side, and having a 
deadly stinging power when used against small animals. In 
t there are very few of the predacious marine animals, 
even not excepting the voracious fishes, that have the temer- 
ty to attack one of the harmless-looking Sea-anemones ; for 
though their darts may not have sufficient power to killa 
large fish, they will, at least, penetrate the thin membranes 
of the mouth and produce a severe stinging, like that of net- 
Note And since these stinging threads may be thrown out 
copiously, and are several inches long, they are very effect- 
wal organs of defence. The inner ends of the threads are 
attached to the free edges of the radiating partitions, and 
the free ends are thrown out simply by the contractions of 
- animal, and consequent expulsion of the fluid contained 
m ts body, which, as it rushes out of the mouth and through 
the loop-holes of the sides, carries with it the threads. When 
ag Actinia is again left in repose, it gradually draws in 
Stinging threads. The little poison-darts, usually called 
hsso-cells, which cover both these threads and the tentacles, 
ve a wonderful structure for organs so minute. They 
