192 LECTURE XT. 



degree of curiosity by their moving up to a 

 shining object to examine it ; and, when in danger, 

 they become suddenly suffused with a decided 

 blush of red, and then eject the contents of their 

 ink-bag, by which they become concealed from 

 observation. 



The oyster closes its shell when it comes in 

 contact with some objects, and opens it on the 

 flowing of the tide, so that its structure is won- 

 derfully adapted to the wants and circumstances 

 of a creature so apparently unconscious of a 

 want, or, if it had one, so incapable of supplying 

 it. 



But let me turn to a higher order of animals ; 

 and I will begin with birds, and their instinct of 

 migration. You are aware that numbers of 

 birds arrive in this country in the spring from 

 far-distant regions, flying over immense tracts 

 of land and sea in one unerring line, and gene- 

 rally doing this in the night. This instinct 

 induces them to seek a warmer climate at one 

 season of the year, and a colder at another. It 

 cannot 'be supposed that the old birds lead the 

 young ones in these migrations, for it has been 

 ascertained that late broods have taken their 

 flight long after their parents have departed. 



