£92 THE DOCTRINE OF DESCENT. 



purpose ? Ought it not rather to be : Every causa 

 engenders a process which again works on towards 

 another process ? The further we go back, the deeper 

 and more general is the grade, and the various ramifica- 

 tions at their peripheral ends have either halted, or 

 arrived at very different grades. 



An objection frequently made against this result of 

 the doctrine of Descent is, that if all are pressing for- 

 ward towards perfection, how is it that, besides the 

 higher, so many lower members of the family are able 

 to maintain themselves, and how can the lower families 

 hold their own against the higher, in the struggle for 

 existence ? In presence of the irrefutable facts of pro- 

 gress, it is enough to point out that the lower forms 

 could and can continue to exist wherever they could 

 find space as well as the other necessaries of life. 

 While they here underwent only slight modifications, 

 elsewhere the needful selection led to more profound 

 metamorphoses ; and on a subsequent geographical dis- 

 placement, the newly transformed beings, accustomed to 

 other conditions of existence, were again able to share 

 sea and land with the stationary species. For as diver- 

 sity is restored now by selection, and the demands for 

 nutriment and other necessaries are likewise different, 

 a partial remission in the struggle must take place. 



The preservation of a great many inferior organisms 

 is evidently favoured by the circumstance that just be- 

 cause they are simpler, their propagation is more easily 

 effected. Hence although, especially in limited districts, 

 amid violent competition of superior varieties, countless 

 species must suffer extirpation, yet the struggle for 

 existence and perfection do not exclude the existence 



