CHAPTER IV. 



EMBRYOLOGY. 



WE will next consider what of late years has 

 become the most important of the lines of evidence, 

 not only in favour of the general fact of evolution, 

 but also of its history : I mean the evidence which has 

 been yielded by the newest of the sciences, the science 

 of Embryology. But here, as in the analogous case 

 of adult morphology, in order to do justice to the 

 mass of evidence which has now been accumulated, a 

 whole volume would be necessary. As in that 

 previous case, therefore, I must restrict myself to 

 giving an outline sketch of the main facts. 



First I will display what in the language of Paley 

 we may call " the state of the argument." 



It is an observable fact that there is often a close 

 correspondence between developmental changes as 

 revealed by any chronological series of fossils which 

 may happen to have been preserved, and develop- 

 mental changes which may be observed during the 

 life-history of now existing individuals belonging to 

 the same group of animals. For instance, the 

 successive development of prongs in the horns of 

 deer-like animals, which is so clearly shown in the 

 geological history of this tribe, is closely reproduced 



