I»S STRUCTURE AND LIFE HISTORIES 



commonly regarded as inheritance, but only a little 

 careful thinking will lead us to see that resemblance 

 and inheritance are by no means synonymous. The real 

 nature of inheritance is well illustrated by tlie inheritance 

 of property by a son from his father. The thing inherited 

 is not an external appearance, but a material substance 

 (land, buildings, a business), which is handed from one 

 to another. So it is in reproduction. That which one 

 generation of plants inherits from another is the substance 

 of the reproductive cells — the protoplasm of the spore, 

 oosperm, tuber, or bulb — plus a certain characteristic 

 organization of this protoplasm, and the effects of its past 

 history. 



170. Inheritance Versus Expression. — That inheritance 

 and expression are not the same thing is plainly shown in 

 the life history of the fern, for the gametophyte clearly 

 derives its living matter by inheritance from the sporo- 

 phyte, and the sporophyte, in turn, its living matter from 

 the gametophyte, and yet the two generations look so 

 little alike that men for centuries knew them both with- 

 out recognizing the fact that they were merely two dif- 

 ferent phases in the life history of the same species of 

 plant. So, often, among human beings, children may 

 bear very little if any resemblance to their parents, but 

 may closely resemble ■ their grandparents. Clearly we 

 do not inherit the color of our eyes or hair, the shapes of 

 our noses, the peculiarities of our voices, or our mental 

 traits from our parents, nor even from our more remote 

 ancestors. What we do inherit is a tiny particle of proto- 

 plasm having a certain characteristic composition, struc- 

 ture, and past history. This protoplasm is capable, under 

 certain combinations of circumstances, of developing 



