THE LIVING WORLD. 
21 
"boasted skill, pales into insignificance. Artisans and engineers as they are, the 
polypes build up from the greatest ocean depths, with matter either secreted 
from their minute bodies or gathered from the waves, mammoth structures cf 
adamantine coral upon which the strongest ships frequently rush, unaware of 
danger until the shivering shock and wreck is at hand. These 
dangerous, though beautiful, structures rise from upheavals of more 
than a thousand fathoms and extend occasionally hundreds of 
miles, with their apexs sometimes a few feet below the ocean sur¬ 
face, and again scarcely level with high tide. These thus become 
dreadful snares for ships, but benefit sometimes results, for upon 
the reefs thus formed seeds scattered by strong winds, or borne 
thither by birds, find lodgment and, even without evidence of soil, 
take root. Sand also accumulates thereon from the restless sea 
waves, until an island is the result, when rich vegetation is ger¬ 
minated, and at length the land thus made becomes habitable. 
Some of the more common types of mollusks are admirably 
illustrated in the accompanying engravings, to which both the 
common and scientific names are attached. Nearly all these crea¬ 
tures are hab¬ 
itants of the 
tropics or 
semi-tropics, 
where they are found in al¬ 
most endless variety. The 
shells found so plentifully 
strewn along the beach, 
washed up by every flow¬ 
ing tide, are all represen¬ 
tatives of the large mol- 
lusk family, some of which 
are of extinct species, whose 
abodes have survived the 
many destructive influences 
of vast periods of time to 
remind us of the marvel¬ 
lous changes that have, oc¬ 
curred in the progression 
towards higher forms of life. 
Passing thus superficially 
over the species pretty gen¬ 
erally known, and to which 
comparatively small interest can attach, we come to the larger and most important 
class' known as the Cephalopoda , a term used to denote a peculiarity of this class, 
which have their tentacles, or more properly feet, arranged in a circle about the head, 
as may be seen in the illustration. Of this class there are several species, among 
which are numbered some of the most beautiful of sea creatures. We have first the 
Argonauta, or Nautilus , the former appellation being derived from the crea¬ 
ture’s habit of lying upon the surface of the sea and being propelled by the 
wind, while its tentacles hang down on either side in fanciful resemblance to 
stone borers (Pholas daclylus). 
WOOD BORER. 
(Pholadi). 
