52 THE FUNCTIONS OF LIFE. 



arransements.* But as the discussion of these and other 

 topics relating to the plans and designs of nature in the for- 

 mation of organic beings requires a previous acquaintance 

 with the details of comparative anatomy and physiology, I 

 shall defer all farther observations respecting them till I 

 have finished the review T propose to take of the several 

 structures and functions of the animal and vegetable econo- 

 my. There are, however, some views that have been en- 

 tertained respecting the procedure of nature in the formation 

 of the different races of animals, which it will be proper to 

 notice in this place, as they will occasionally be referred to 

 when the facts that more particularly illustrate and support 

 them come to be noticed. -^ 



An hypothesis has been advanced that the original crea- 

 tion of species has been successive, and took place in the or- 

 der of their relative complexity of structure; that the stan- 

 dard types have arisen the one from the other; that each 

 succeed in g form was an improvement upon the preceding, 

 and followed in a certain order of development, according 

 to a regular plan traced by the great Author of the universe 

 for bestowing perfection on his works. This gradation- of 

 structure was necessarily accompanied by a gradation of fa- 

 culties: the object of each change of type being to attain 

 higher objects, and to advance a farther step towards the ul- 

 timate ends of the animal creation. Many apparent anoma- 

 lies which are inexplicable upon any other supposition, are 

 easily reconcileable to this theory. The developments of 

 structure belonging to a particular type being always pro- • 

 spective, are not completed in the inferior orders of the 

 group formed upon that model, but remain more or less 

 imperfect, although each organ always fully answers the par- 

 ticular purpose of the individual animal. But it sometimes 

 happens that the imperfection of an organ is so great, in con- 

 sequence of its development having proceeded to a very small 



* Mr. M'Leay is the author of this ing-enious theory, which he has de- 

 veloped in his " Horx Entomologlca;" and which appears to be verified to a 

 great extent by the modern discoveries in comparative anatomy. 



