HEREDITY 481 



for when the parent is developing, a residue of unspecialised 

 germinal material, retaining the heritable qualities in their 

 intactness, is kept apart, and will eventually give rise to the 

 germ-cells which form the starting-point of the child. As 

 Weismann put it: In each development a portion of the 

 specific germ-plasm contained in the parent egg-cell is not 

 used up in the construction of the body of the offspring, 

 but is reserved unchanged for the formation of the germ-cells 

 of the following generation. So it comes to be that the 

 parent is rather the trustee of the germ-plasm than the 

 producer of the child. In a new sense the child is a chip 

 of the old block. Or, as Bergson puts it, in less static 

 metaphor, " life is like a current passing from germ to 

 germ through the medium of a developed organism ". It 

 appears that too rigid a contrast has been made between 

 body-cells and germ-cells ; for groups of body-cells in plants, 

 sponges, polyps, worms, Tunicates, and various other groups 

 are able to develop into perfect organisms. It is safer to 

 say that the germ-cells are those cells which carry the whole 

 inheritance without allowing any of it to find expression 

 until appropriate conditions and stimuli are forthcoming. 

 They carry the whole inheritance in a form little liable to 

 extrinsic influence and yet readily admitting of development. 

 The general idea of germinal continuity is one of the most 

 important contributions to post-Darwinian biology. It ac- 

 counts for the inertia of the main mass of the inheritance, 

 which is carried on with little change from generation to 

 generation. For men do not gather grapes off thorns or 

 figs off thistles. Similar material to start with ; similar con- 

 ditions in which to develop; therefore like begets like. 



(&) The second role of the hereditary relation is that it 

 allows of the emergence of the new and of the handing-on 



