134 LIFE AND HER CHILDREN. 
beautiful shell with its pearly chambers is found and 
brought to decorate our homes. 
And here we must take leave of the mantle- 
covered animals. We have followed them, though 
very imperfectly, from the " poor patient oyster," 
through their gradual rise in power ; till we leave 
them as dreaded conquerors, in the sharp -beaked 
octopus and the terribly armed calamary. We might, 
if we had ventured on the dangerous sea of conjecture, 
have started still earlier, and linked their simpler forms 
to those of the lower worms. But till more is known, 
this course might have led us astray, and it is safer 
to content ourselves with marking how life has 
O 
gradually filled the ocean and the land with specially 
fitted forms of mollusca, having all a distinctive 
nationality which separates them from the other 
divisions of Life's children ; so that the octopus, the 
cuttle-fish, and the nautilus, stand as undoubtedly at 
the head of one great plan of animal life, as the ants 
do at the head of the insects, or man at the head of 
the vertebrates. We shall now have to hark back 
again, and in inquiring of the worm whence he 
comes, and how he lives, start on a totally different 
track, which will lead both by land and water, 
through the forms of the shrimp, and crab, and 
lobster, to the aerial and fairy -like insects which 
form so large a portion of the life upon our globe. 
