THE DARWINIAN THEORY. 



101 



chance in the development or perfection of the organs or instincts 

 of created beings. His followers say that the adoption of his 

 theory would leave the doctrines of final causes, utility, and 

 special design just where they were before. 



Darwin made so much of the resemblance amongst the 

 young of vertebrate animals that he thought it probable all the 

 members in the four great classes, viz. Mammals, Birds, Eep- 

 tiles, and Fishes, were the modified descendants of one ancient 

 progenitor, which was furnished in its adult state with branchiae, 

 had a swim-bladder, four simple limbs, and a long tail fitted for 

 aquatic life. 



In regard to the resemblances between young animals, 

 Agassiz states that the embryo of the American Freshwater 

 Turtle and the embryo of the Snapping Turtle resemble one 

 another far more than the different species of the former in 

 their adult state ; a young Snake resembles a young Turtle or a 

 young bird much more than any two species of Snakes resemble 

 one another ; and yet not a single fact can be adduced to show 

 that any one egg of an animal has ever produced an individual of 

 any species but its own. 



Dr. Asa Gray sums up that Darwin's theory, leaving man out 

 of the question, very well accords with the great facts of zoology 

 and comparative anatomy, or goes far to explain both the physio- 

 logical and structural gradations and relations between the two 

 kingdoms, and the arrangement of all their forms in groups 

 subordinate to groups, all within a few great types ; that it 

 reads the riddle of undeveloped organs and of structural con- 

 formity, of which no other theory has offered a scientific expla- 

 nation, and supplies a ground for harmonizing the two funda- 

 mendal ideas which naturalists and philosophers conceive to 

 have ruled the organic world, though they could not reconcile 

 them, viz. adaptation to purpose and to the conditions of existence, 

 and the Unity of Type. While the theory seems inadequate to the 

 task it so boldly assumes, it must be remembered that the more 

 important objections relate to questions on which we are con- 

 fessedly ignorant. Those who imagine it can be easily refuted 

 and cast aside must, he says, have imperfect or very pre- 

 judiced conceptions of the facts concerned and of the questions 

 at issue. 



