iio6 LIFE : OUTLINES OF GENERAL BIOLOGY 



legitimacy — indeed necessity — of the distinction between Individual 

 Development (Ontogeny) and Racial Evolution (Phylogeny). 



Organic Evolution may be defined as a natural process of con- 

 tinuous racial change in some observable direction, in the course of 

 which distinctively new individualities emerge and are established, 

 alongside of, or in place of the originative stock. When several dif- 

 ferent parts of the organism are evolving simultaneously, it will be 

 necessary to say "in an observable direction or in several directions". 



Our knowledge of the factors operative in Organic Evolution is 

 still very young, and obviously incomplete, but so far as is clearly 

 seen at present, it is a process of varying and entailing, sifting and 

 singling. There are originative factors that bring about novelties 

 or new departures (variations and mutations). Then there is a sieve 

 interposed by the conditions of heredity, which may be defined as 

 the relation of genetic continuity between successive generations. 

 For it is plain that an organic variation cannot be of direct racial 

 importance unless it is hereditarily continued on (transmitted is a 

 more than dubious term) as part of the specific organisation. The 

 new departures are sifted in the struggle for existence in the widest 

 sense, including, as Darwin clearly recognised, the endeavours the 

 organism makes in its will to live — endeavours which are sometimes 

 so precise that they imply a testing of a novel quality which has 

 arisen. There is no warrant for thinking of organisms as passive 

 pawns; they play the game, thus sharing in their own evolution, 

 as Prof. James Ward was wont to insist. To change the meta- 

 phor, the organism plays its "hand" of hereditary cards, the shuf- 

 fling of which occurred in the early life of the germ-cells, up to and 

 including fertilisation. Besides Nature's sifting or Natural Selection 

 there are various forms of Isolation which are ancillary to species- 

 forming. That is to say, there are many different ways in which 

 the range of inter-crossing may be narrowed, thus bringing about 

 inbreeding or endogamy, which tends to fix characters. And this 

 may alternate with a period of out-breeding or exogamy, which 

 tends to promote variation. As we have said, the factors in Organic 

 Evolution remain very uncertain; but what is meant is that there 

 has been an age-long process comparable to that which is known 

 in the production of breeds of domesticated pigeons from the wild 

 ancestral Rock Dove, or the races of cultivated wheat from the 

 wild wheat of Mount Hermon. In both cases there have been pro- 

 cesses of breeding and weeding, tr3dng and testing, singling and 

 sifting, but while Man holds the sieve in domestication and cultiva- 

 tion, this comes about in Nature in the course of the struggle for 

 existence, which rises into an endeavour after well-being. Hence, 

 despite their likeness, the necessity of keeping Natural Selection 

 and Artificial Selection as distinct terms, as Darwin showed. But 

 one of the differentiating features between Organic Evolution and 



