606 THE BEGINNINGS OF LIFE. 



which had been previously looked upon as unaccount- 

 able anomalies 1 / We have already pretty fully pointed 

 out to what an extent the views advocated in these 

 volumes are confirmed by the wide application of 

 such tests. A few apparent anomalies, however, still 

 remain for further consideration, which, although quite 

 irreconcilable with generally-received doctrines, may, 

 perhaps, be cleared up by the light derived from new 

 views. 



How, it may be asked, is the possession by living 

 things of an internal tendency to develop, consistent 

 with the existence of such multitudes of low organisms 

 in the present day and in past geologic ages? And 

 how is it consistent with what we know concerning 

 the Persistence of Types ? 



We have already 2 pointed out the almost insuperable 

 difficulties in accounting for the present existence of 

 lowest organisms in accordance with the old hypothesis. 

 This, as expressed by Mr. Darwin 3 , is, that c all the 

 living forms of life are the lineal descendants of those 

 which lived long before the Silurian epoch.' On the 

 other hand, what has been made known in this work 

 now relieves us from all difficulties concerning the 

 existence of very low organisms at the present day 

 our Ephemeromorphs. We may safely discard all 

 notions concerning their pre-Silurian pedigree, and 



1 ' Contrib. to the Theory of Nat. Selection,' 1870, p. 45. 



2 See pp. 103-108. 



3 ' Origin of Species,' 5th ed., p. 578. 



