THE BEGINNINGS OF LIFE. 589 



^ the average result ^ being, ^ that on previous complica- 

 tions of structure wrought by previous incident forces 

 new complications are continually superposed by new 

 incident forces. And hence simultaneously arises ia- 

 creasing heterogeneity in the structures of individuals, 

 in the structures of species, and in the structures of the 

 earth's Flora and Fauna ^/ But with this constant al- 

 ternation of changes of all kinds, to which every single 

 environment on the face of the earth must have been 

 subjected, is it to be deemed possible that the descend- 

 ants of simple and little differentiated organisms could 

 have reproduced their like, without any considerable 

 alteration, during an unbroken lineal descent through 

 the millions and millions of years which must have 

 elapsed since the first evolution of life upon our planet ? 

 Mr. Spencer seems to think this is possible, owing to 

 the fact that occasionally ' new influences are escaped 

 by the survival of species in the unchanged parts of 

 their habitats, or by their spread into neighbouring 

 habitats which the change has rendered like their 

 original habitats, or by both.' But, independently of 

 the impossibility of eluding the all-pervading influence 

 of some of the causes of change above cited, it 

 seems to me absolutely incredible that, through this 

 long lapse of ages, some of the lineal descendants of 

 so many specific forms should have succeeded in 



1 This was also, in the main, the view advocated by Geoffroy St. Hi- 

 laire in his ' Eludes progressives d'un Naturaliste/ p. 107. See also 

 • Mem. de I'Acad. des Sciences,' 1833. 



