5-2 



NATTRAL HISTORY. 



[lesson X. 



2. I low do the Molluscous animals differ 

 from the Vertebrate ? 



o. Name the \arious classes of Mollusca. 



4. (Jive examples fro-ii each class. 



5. State the peculiarities of the Mollus- 

 cous animals. 



i. What is tin- meaning of the terms 

 applied to each class .' 



7. What is an ti/ii'rculuni ? 



8. Kxplaiu uli.it is meant hy a univalve 

 and bivalve. 



LESSON X. 



EACH great division of the Animal Kingdom presents some generality of form. We 

 have observed the peculiarities of the first t\\o divisions, and we have now to notice 

 those presented by the third ANIMALIA AKTICULATA, or animals with articulated 

 bodies. That great naturalist, Cuvier, observed that "this third general form is as 

 well characterised as that of Vertebrata ; the skeleton is not internal, as in the latter; 

 neither is it wanting, as in the Moliusca. The articulated rings which encircle the 

 body, and frequently the limbs, supply the place of it ; and as they are usually hard, 

 they furnish all the necessary support for the muscles by which the body is moved ; 

 so that among the animals, as is the case of the Vertebrata, those which have limbs 

 are able to w.tlk, to s^im, or to Hy. Thus they have some general resemblance, more 

 particularly in their internal organisation, although in most respects they differ from 

 each other to the utmost degree." 



QUESTIONS. 



138. T. In what respect do all articu- 

 lated animals resemble each other most? 

 P. In their nervous system. 



MO. T. Is there anything peculiar 

 in it ? 



P. Yes, the brain, which is very small, 



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is placed over the oesophagus or gullet, and 

 * t'iy. H. Nervoua iyiniof Carubus Clftibnt- 



..MII! the ci.Hiii of g;iii;:ll;i Connected by 

 double chord. 



supplies nerves to all the parts near to the 



head, and two chords whi'-h encircle the 



; oesophagus are continued along the abdo- 



1 men, and connected at intervals by ganglia, 



j from which the r.ervcs are sent to the 



various parts of the body and limbs. 



j 140. T. What oflice does a ganglion 

 perform ? 



P. It seems to act like a brain, con- 

 ferring sensibility on the parts with which 

 it is intimately connected. 



HI. T. Are there any other pecu- 

 liarities to be observed in the Articulata .' 



/'. Yes, their jaws arc invariably lateral, 

 and shut together like a pair of scissors 

 that is, horizontally, and not upwards and 

 downwards ; and besides this, we observe 

 that they have not any distinct organ of 

 smell. 



142. T. How are the articulated ani- 

 mals classed ? 



P. Into four principal classes ; 1. The 

 ANNELIDES, or red-blooded worms. 2. The 

 CRUSTACEA, or hard-coated animals ; 3. 

 ' l ^ AEACHDA, <>r animals like spiders ; 

 4. The INSECT A, or insects. 



