168 DR. H. B. FAXTHAM 



do occur, assuredly iiidividiials thus characterised will 

 have the best chance of being preserved in the strng^gle 

 for life; and from the strong- principle of inheritance, 

 these will tend to prodnce offspring similarly charac- 

 terized. This principle of preservation or the snrvival 

 of the fittest, I have called Xatnral Selection. It leads 

 to the improvement of each creatnre in relation to its 

 organic and inorganic conditions of life, and, consequent- 

 ly, in most cases, to what must be regarded as an advance 

 in organisation. Nevertheless, low and simple forms will 

 long endure, if well fitted for their simple conditions of 

 life. 



We may now attempt to summarise Darwin's work in 

 general terms. Evolution or the doctrine of descent may 

 be briefly defined as progress involving differentiation, 

 or as the alteration of the average characters, either of 

 the whole of a species or of groups of its members, from 

 generation to generation in a constant manner, the result 

 being that they are so different from what they were 

 before, that a new species arises. The said species has, 

 however, its own definite characters, and the test of 

 validity of a species is that it breeds true, the offspring 

 not reverting to the marked characters of the ancestral 

 stocks, but retaining the modified characteristics that are 

 the result of the differentiation from those ancient 

 features. 



Evolution imi)lies (a) raw materials in the form of 

 variations; (b) an arrangement for securing the in- 

 heritance of some of these; and (c) a directive mechanism 

 for securing consistency and effectiveness of racial change. 



Heredity, here referred to, means the transference of 

 similar characters from one generation of organisms to 

 another, a |)rocess effected by means of the germ-cells. 



As regards Variations, the existence of variations is an 

 observed fact, for individuals of flie same parentage are 

 not identical. These variations may be small, fluctuating 

 and continuous, or large, sudden and discontinuous. 



