2 



POPULAK CO^CHOLOGY. 



gradual increase and advancement to its perfect state, in- 

 cluding in his researches the formation of its shell, and 

 the mode by which it receives enlargement and colour, he 

 will here again find this study as interesting as that of any 

 portion of the created kingdom. 



Conchology* is the familiar term employed for this 

 branch of Natural History, but, when connected also with 

 that of the animals, the term Malacology is used. In 

 pursuing this pleasing study, whether an extended or 

 limited view be taken, it is necessary, in the first place, to 

 know something generally of the animals, their growth, 

 the mode by which they form their shells, their place of 

 residence, and habits, before entering upon a minute and 

 classified division. The present chapter will therefore 

 have these objects in view. 



The animals which inhabit and form shells are called 

 Mollusca] , and, as their name signifies, have a soft body, 

 most of them beins: entirelv destitute of bones, thouo-h 

 some are provided with internal shells, more or less per- 

 fectly formed; some species of slug, for instance, have 

 internally a rudely shaped hard body, and others a mass 

 of small grains. The cuttle fish also, of the class Cepha- 

 lopoda, have an internal support in the form of a pen. To 

 compensate for the apparent deficiency in this respect, and 

 to enable them to provide themselves with a defence 

 against any injury to which they might be liable from so 

 delicate a structure, they have been furnished with an 

 external skin or envelope, covering them more or less 

 completely, and from which a liquid exudes, which, on 

 exposure to the air or water, hardens into shell ; thus 



* From conch i/li on, Gr., or concha, Lat , a shell, and logos, Gr., a 

 discourse. 



f From mollis, Lat., soft, and esca, Lat., flesh. 



