72 Heredity and Environment 



develops out of the germ, and the organization of the germ deter- 

 mines all the possibilities of development of the mind no less than 

 of the body, though the actual realization of any possibility is 

 dependent also upon environmental stimuli. 



II. Hereditary Differences 



There are many exceptions to the general rule that children 

 resemble their parents ; indeed no child is ever exactly like a par- 

 ent and the points in which they differ are known generally as 

 variations. These variations are of two kinds, those which are 

 caused by a different germinal constitution and are therefore in- 

 herited and those due to environmental differences which are not 

 inherited. Sometimes inherited variations are due to new com- 

 binations of ancestral characters, sometimes they are actually new 

 characters not present so far as known in any of the ancestors, 

 though even such new characters must arise from new combina- 

 tions of the elements of old characters, as we shall see later. 



i. New Combinations of Characters. — In all cases of sexually 

 produced organisms new combinations of ancestral characters are 

 evident. Usually a child inherits some traits from one parent 

 and other traits from the other parent, so that it is a kind of 

 mosaic of ancestral traits. Such inheritance, bit by bit, of this 

 character from one progenitor and that from another was de- 

 scribed by Galton as "particulate" (Fig. 23) and is known today 

 as "Mendelian." On the other hand Galton supposed that in some 

 instances a child might inherit all or nearly all of his traits from 

 one parent, a thing which is most improbable ; such inheritance he 

 called "alternative"* (Fig. 23). 



In other cases the traits of the parents appear to blend in the 

 offspring, as for example, in the skin color of mulattoes; such 



* It is necessary to distinguish between alternative inheritance of a single 

 character (Mendel) and this supposed alternative inheritance of all char- 

 acters (Galton). 



