30 HERBERT SPENCER AND 



pre-localization may and does exist. From what I have 

 said, I think it is clear that this pre-localization is a 

 secondary and derived condition, not a primary one. 



For if it were primary, it would be specially well 

 marked in the eggs of animals which, on other evidence, 

 we regard as primitive, but this is not the case. On 

 the contrary, it is specially well marked in animals which 

 we "have every reason to suppose are much modified, 

 either in their larval stages, or in their adult stages, or 

 in both. 



If then it is a secondary condition, and if this condition 

 has been acquired several times over, within the limits 

 of a single class, the germ-plasm has been modified and, 

 as far as we can judge, is still undergoing modification 

 in a large number of cases. It is always having the 

 characters, many of them adaptive characters, of the 

 adult thrown back into itself, and conversely, as its 

 constitution is altered, it must reproduce these characters 

 in every somatic generation to which it gives rise. 



We are confronted with the old question, as old as the 

 time of Aristotle, whether the egg gives rise to the fowl 

 or the fowl to the egg. 



Weismann would answer the question in this way. 

 The germ-plasm is variable, because the biophors com- 

 posing it are affected by slightly different conditions of 

 nutrition, temperature, &c., and vary. Their variations 

 induce further variations in the determinants, which 

 control the structure of each separately variable part of 

 the organism at all stages of its existence. Therefore 

 the organism varies, and every beneficial variation, at 

 every period of life, will be selected. Natural Selection 

 ensures that only those forms shall survive whose germ- 

 cells contain favourable variations. What is apparent 

 to us is the preservation of favourable modifications in 

 adult (or larval) individuals. What really is preserved 

 is the kind of germ-plasm that has produced those favour- 

 able modifications, and as this is handed on from selected 



