MOLLUSKS. 320 
Fig. 254,—Clio Borealis, 
with teeth, calculated to tear in pieces the minute ani- 
mals on which it feeds. It has also a very effective ap- 
paratus for securing its prey, consisting of six tentacula 
of a reddish color. On examining one of these with a 
microscope, this color is found to be occasioned by red 
points arranged with great regularity. On magnifying 
these still farther, each point is seen to be a collection of 
about twenty suckers on the ends of as many stalks. 
Each collection is in a sort of sheath, and can be pro- 
truded from it. There are on all the tentacula about 
three hundred and sixty thousand of these suckers, con- 
stituting an apparatus for prehension more extensive, in 
proportion to the size of the animal, than any other to be 
found in the whole animal kingdom. 
Questions. —What is the significance of the name of the third sub- 
kingdom of animals? What are naked Mollusks? What is said of 
the use of the covering which most of them have? Of what is it 
composed? What is said of the proportions of the constituents? How 
is the shell formed? What are the two kinds of shells? What is said 
of the changes which shells undergo in growing? Whatis said of the 
locomotion of Mollusks? What is said of the foot, and its various 
uses? What is the byssus? What provision for locomotion is there 
in most of the Mollusks that inhabit bivalve shells? What in those 
that are similar in structure, but have no shell? What is the speciak 
destiny of Mol!lusks? What is said of their breathing apparatus? 
What of their blood, and its circulation? What are the two grand 
divisions of Mollusks? What are the groups in the first division, and 
their characteristics? Of the Cephalopods, what shelly species exist 
at the present time? What is said of the Ammonites? Describe 
the structure and habits of the Cuttle-fish. What is sepia? What 
