PHYLOGENY. 43 



that particular organisms have arisen by the gradual modifi- 

 cation of their predecessors, which is furnished by fossil 

 remains. That evidence is daily increasing in amount and in 

 weight ; and it is to be hoped that the comparison of the 

 actual pedigree of these organisms with the phenomena of 

 their development may furnish some criterion by which the 

 validity of phylogenetic conclusions, deduced from the facts 

 of embryology alone, may be satisfactorily tested. 



