GERMINAL SELECTION 463 



the germinal selection would still continue, and thus we can 

 picture to ourselves a modus operandi whereby the useless 

 organ would dwindle more and more. 



Similarly, every one admits that the huge canines of various 

 mammals have evolved from relatively small teeth in the same 

 position. For many generations natural selection would favour 

 variants with larger canines — i.e. those in whose germ-plasm 

 or inheritance canine-determinants varying in the direction oi 

 greater size and strength of teeth were predominant. " The 

 moment that these come to predominate in the germ-plasm of 

 the species, at once the tendency. must arise for them to vary 

 still more strongly in the plus direction, not solely because the 

 zero-point has been pushed further upwards, but because they 

 themselves now oppose a relatively more powerful front to 

 their neighbours — that is, actively absorb more nutriment, and 

 upon the whole increase in vigour and produce more robust 

 descendants. From the relative vigour or dynamic status of 

 the particles of the germ-plasm an ascending line of variation 

 will thus spontaneously arise, precisely as the facts of evolution 

 require." Furthermore, if we admit this consideration we 

 can in some measure understand why the ascending line of 

 variation often tends to go too far ; and sometimes does go 

 too far when the check of natural selection is removed by the 

 artificial conditions of domestication. 



Yalue of the Theory. — Weismann emphasises the following, 

 among other advantages of the theory of germinal selection, 

 It suggests an interior mechanism which interprets the occur- 

 rence of definitely directed variations, the occurrence of appro- 

 priately useful variations at the right place and time, the di- 

 minution of organs below the level touched by personal selection 

 or its cessation (panmixia), the occasional exaggeration of organs 

 beyond the limits of demonstrable utility, the simultaneous 

 occurrence of many similar variations, and so on. 



It must remain a question for personal judgment whether 



