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CHAPTER XL 



ENIGMAS AND THEIR SOLUTION. 



LET us now analyse the processes in the 

 marvellous transformations of the embryo 

 during its growth, and endeavour to discover 

 their significance and bearing on the general 

 question of evolution. 



We see that the embryo of a mammal 

 develops, during at least the earlier phases 

 of its growth, in the type of its antecessor, 

 and that at a certain stage, which varies in 

 different genera but is uniform in every race, 

 what seems a new force intervenes and begins 

 to evolve some organ in the type of the 

 successor, which is not that of the antecessor, 

 while some other organ is being formed in 

 the type of the antecessor, which is not that 

 of the successor. Thus there seem to be 

 two forces of growth developing the embryo 

 in different types, and in consequence the 

 embryo in this stage is neither wholly in the 

 type of the antecessor nor of the successor. 



