32 TERRESTRIAL ADAPTATIONS. 



not to believe that the watch had been contrived 

 to accommodate itself to the solar day. We have 

 at least ten thousand kinds of vegetable watches 

 of the most various forms, which are all accommo- 

 dated to the solar year ; and the evidence of con- 

 trivance seems to be no more capable of being 

 eluded in this case than in the other. 



The same kind of argument might be applied 

 to the animal creation. The pairing, nesting, 

 hatching, fledging, and flight of birds, for 

 instance, occupy each its peculiar time of the 

 year ; and, together with a proper period of rest, 

 fill up the twelve months. The transformations 

 of most insects have a similar reference to the 

 seasons, their progress and duration. " In every 

 species" (except man), says a writer* on animals, 

 " there is a particular period of the year in which 

 the reproductive system exercises its energies. 

 And the season of love and the period of gestation 

 are so arranged that the young ones are produced 

 at the time wherein the conditions of temperature 

 are most suited to the commencement of life." It 

 is not our business here to consider the details of 

 such provisions, beautiful and striking as they 

 are. But the prevalence of the great law of 

 periodicity in the vital functions of organized 

 beings will be allowed to have a claim to be con- 

 sidered in its reference to astronomy, when it is 



* Fleming. Zool. i. 400. 



