226 EVOLUTION IN BIOLOGY vi 



and of the CarnivQra have been almost as closely 

 followed through the Tertiary deposits; the gra- 

 dations between birds and reptiles have been 

 traced; and the modifications undergone by the 

 Crocodilia, from the Triassic epoch to the present 

 day, have been demonstrated. On the evidence of 

 paleontology, the evolution of many existing forms 

 of animal life from their predecessors is no longer 

 an hypothesis, but an historical fact ; it is only the 

 nature of the physiological factors to which 

 that evolution is due which is still open to dis- 

 cussion. 



[At page 209, the reference to Erasmus Darwin does not do 

 justice to that ingenious writer, who, in the 39th section of the 

 Zoonomia, clearly and repeatedly enunciates the theory of the 

 inheritance of acquired modifications. For example: "From 

 their first rudiment, or primordium, to the termination of their 

 lives, all animals undergo perpetual transformations ; which are 

 in part produced by their own exertions in consequence of their 

 desires and aversions, of their pleasures and their pains, or of 

 irritation, or of associations ; and many of these acquired forms 

 or propensities are transmitted to their posterity." Zoonomia I., 

 p. 506. 1893.1 



