NATURAL THEOLOGY. 335 



modified with a reference to utility founded on 

 the condition of the offspring. In quadrupeds, 

 the young animal draws its nutriment from the 

 body of the dam. The male parent neither does, 

 nor can contribute any part to its sustentation. 

 In the winged race, the young bird is supplied by 

 an importation of food, to procure and bring home 

 which, in a sufficient quantity for the demand of a 

 numerous brood, requires the industry of both pa- 

 rents. In this difference, we see a reason for the 

 vagrant instinct of the quadruped, and for the 

 faithful love of the feathered mate. 



