88 EVOLUTION OF TO-DAY. 



in accordance with the evidence. Upon examina- 

 tion, it is found to fit the facts marvellously well, and 

 to do away with many perplexing problems. With 

 careful study this theory has been found to offer a 

 simple explanation to many classes of facts which 

 had hitherto been troublesome puzzles. The theory 

 has, it is true, raised certain difficulties of its own, 

 for it has found itself unable to explain every thing. 

 The problem of serial homology, and the difficulty 

 of understanding the degradation of organs to a 

 rudimentary condition, and their final disappearance, 

 are the chief ones, but even these are difficulties for 

 Darwin's explanation of evolution, and not for the 

 descent theory itself. Admitting, however, their full 

 force, they are not sufficient to offset the great ad- 

 vantages offered by the descent explanation. No 

 one thoroughly acquainted with the organic world 

 hesitates to say that the theory of descent must be 

 admitted as a factor, though perhaps not the only 

 .factor. As a conclusion from the study of classifi- 

 cation, it seems that we must either accept evolution 

 as the explanation of the bond of union in the 

 organic world, or wait for some other better theory, 

 of which the descent idea will doubtless form a 

 part. 



