214 OUTLINES OF EVOLUTIONARY BIOLOGY 



individuals arise by some process of reproduction from- pre-exist- 

 ing parent individuals. This is represented in the upper parts 

 of both diagrams, where a 18, b 17, c 14, d 15 and 

 e i 5 ; on each side, are supposed to represent small groups of 

 individuals of the species A B C D and E respectively, each 

 group being descended from some common ancestor (or pair of 

 ancestors) which itself belonged to the species. 



The study of this diagram is alone sufficient to afford strong 

 presumptive evidence in favour of the view of the evolutionist as 

 against that of the upholder of special creation, for the evolu- 

 tionist in his imagination extends backwards into the past the 

 processes which he sees taking place constantly at the present 

 day, and endeavours to account for the origin of species in 

 accordance with what he knows to be true of the origin of 

 individuals. In other words, the diagram expressing the idea of 

 organic evolution is consistent throughout, whereas that which 

 represents the idea of special creation is made up of two incon- 

 gruous portions, and is therefore less likely to be correct. The 

 . great weakness of the doctrine of special creation, however, lies 

 in its failure to explain countless facts of comparative anatomy, 

 embryology, geographical distribution and palaeontology, all of 

 which are readily explicable in terms of evolution. We shall 

 deal with some of these facts in subsequent chapters. 



It is obvious, then, that in order to be logically consistent the 

 evolutionist need not postulate more than a single starting point 

 for the evolution of the whole organic world, though he is not 

 obliged to limit himself in this way should evidence be forth- 

 coming that there has been more than one starting point. This 

 brings us to the consideration of the extremely difficult and at 

 present quite insoluble problem of the origin of the first living 

 organisms. 



Here again we may first inquire whether our experience of what 

 takes place at the present day throws any light upon the problem. 

 Many people in the past have held, ami some fe^w s&ll toaintain, 

 tha't* living thin^in*ay, x even n'pV, arise from not-living matter. 

 This is known as the doctrine f " Spontaneous Generation " or 

 abiogenesis. One of the earliest expressions of this idea is met 

 with in classical mythology, in the story of the birth of Aphrodite 

 from the sea-foam ; and Vergil, in the Georgics, accepts the prin- 

 ciple involved therein apparently in perfectly good faith. 



Vergil's account of the manner in which a swarm of bees may 



