246 MOLLUSCA. 



mysterious movements."* Thus does God care for 

 the meanest of His creatures : thus is " His tender 

 mercy over all His works !" 



The mode by which Bivalve shells are closed and 

 opened is curious. They are connected, in the 

 hinder part, by a hinge, formed differently in differ- 

 ent genera. The most simple is that of 



Ostrea,-\ the Oyster. 



A perpendicular mass of highly elastic fibres is 

 interposed between the two hinder edges, so dis- 

 posed, that when the shells are forcibly pressed to- 

 gether, it is squeezed into a very short compass, 

 but powerfully expands immediately the force upon 

 the valves is removed, and forces them open to a 

 greater or less extent. This is the apparatus for 

 opening the shells. 



The closing of them by overcoming the expansive 

 force of the hinge-ligament, is provided for in a strong 

 elastic muscle, which passes perpendicularly across 

 from the middle of one shell to the opposite. The 

 fibres of this muscle contracting with immense force, 

 resist the opening ligament, and that so powerfully, 

 as is well known to every eater of Oysters, that the 

 most violent efforts to open the shells are vain 

 until the breaking away of the edges affords an aper- 

 ture for the knife, to separate the contracting fibres. 



In speaking of the Gasteropoda, we have endea- 

 voured to describe the mode in which the growth 



* Jones, Anim. Kingd. p. 378. t Its Latin name. 



