CHAPTER I. 



ORGANIC EVOLUTION. 



THE geological record of our planet informs 

 us that life first appeared on the earth 

 in simple forms ; that these simple forms 

 were, in the course of ages, succeeded by 

 numberless varieties of plants and animals, 

 whose organisation, as new types success- 

 ively appeared, became, as a general rule, 

 more and more highly specialised, until at 

 last Man appeared upon the scene. 



Embryology seems to tell a similar story. 

 The embryo of every mammal, including 

 man, presents in its growth from the 

 germ - cell to maturity, phases similar to 

 those in the embryos of other organisms 

 less highly specialised ; in other words, 

 the foetus of each succeeding type re- 

 sembles, in at least the earlier stages of 

 its growth, that of its antecessor, and only 

 as maturity approaches does it assume its 

 own special characteristics. 



