MOLLUSKS. 323 



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 ? What is 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 special 

 destiny of Mollusks ? 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 



