134 DARWINISM AND HUMAN LIFE 



by a curious contrivance, that part of the original 

 leaven is not mixed up with the dough, but is 

 carried on unaltered within the loaf, carefully 

 preserved for use in another baking. Nature is 

 the baker, the loaf is a body, the leaven is the germ- 

 plasm, and each baking is a generation. 



Picture the long runner of a strawberry, bearing 

 rooted, flowering plants at intervals : the runner 

 may represent the continuous line of germ-cells, 

 the flowering plants are the individuals, and the 

 relation between them is the relation of genetic 

 continuity, which we call heredity. 



It will be obvious that this concept of germinal 

 continuity is very different from Darwin's pro- 

 visional hypothesis of pangenesis, according to 

 which the germ-cells have their peculiar virtue of 

 reproducing like from like because they become 

 the storehouses of representative gemmules liber- 

 ated from the various organs of the body. Although 

 the hypothesis did not at the time obtain favour 

 and is less acceptable now than ever, it is interesting 

 to note, as Prof. Strasburger points out, that it in- 

 cluded the favourite modern idea of invisible units 

 as the carriers of particular hereditary characters. 



(5) Critical Attitude in regard to Various Con- 

 clusions. Another change is seen in the critical 

 attitude which is now taken up in regard to 

 various sets of facts, or alleged facts, relating to 

 inheritance, which were once accepted without 

 question. Thus Darwin said a good deal about 

 reversion ; but many phenomena labelled " rever- 

 sion " have received a different interpretation, and 

 some of the leading authorities on heredity have 

 ceased to use the term. It is difficult to find a 

 scientific worker who believes in what many 



