140 EVOLUTION OF TO-DAY. 



mental law of embryology, that the development of 

 the individual is a repetition of past history. It is 

 supported by the comparison of embryology with 

 paleontology, by the complete harmony amid the 

 *" discord coming from its comparison with the hypo- 

 thetical history which classification teaches, and by 

 the fact that it not only enables the student to ex- 

 plain difficulties, but also to make predictions the 

 best test of any scientific theory. Considering it, 

 therefore, as practically demonstrated, we proceed 

 to the consideration of its meaning. 



2. The Significance of the Parallel between Embry- 

 and Past History. 



The real question as to whether embryology forms 

 an argument for evolution, concerns the explanation 

 we can give to the parallel which has been under 

 consideration. The embryologist assumes that the 

 parallelism proves evolution, and busies himself in 

 studying details and constructing from the evidence 

 as correctly as possible the genealogical history of 

 animals. Before following him into this field, we 

 must first take a more general view of the matter 

 and discover the true significance of the principles 

 on which he works. 



In reality the teachings of embryology, as ex- 

 pounded by its students and as verified by modern 

 research, form the strongest direct argument in 

 favor of the theory of descent. The parallel in 

 question is certainly one of the most marvellous dis- 

 coveries ever made ; a discovery which would never 

 have been dreamed of from a priori grounds. Why 



