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 
