THE LAWS OF HEREDITY 



figs on fig trees. We would be astounded were 

 the conditions reversed; and this evidences the 

 almost axiomatic character of the great funda- 

 mental law of heredity, and its universal accept- 

 ance as a part of common knowledge. 



MINGLING MODIFIED GEKM-PLASMS 



In all this, then, we are expositing the idea 

 that the racial germ-plasm conveys the record of 

 past environments and predetermines the char- 

 acteristics and qualities of the organism that may 

 grow from that germ-plasm. As thus far viewed, 

 therefore, the facts connoted in the familiar 

 phrase "like parent, like child " are scarcely 

 more mysterious than the fact that successive 

 cups of water dipped from the same stream 

 should be like one another. 



But there is a vastly complicating fact which 

 we have thus far purposely ignored the familiar 

 fact, namely, that each higher organism is not the 

 offshoot of a single parent, but a product of the 

 union of two parents. 



Be it plant or animal, every individual above 

 the very lowest strata of organic-like owes its 

 being to the union of two germ-cells. It represents 

 the commingling of two strains of racial germ- 

 plasm. Pollen grain unites with ovule in the case 

 of the plant; sperm-cell with ovule in the case of 

 the higher animal; and each type of cell conveys 

 its own coterie of hereditary potentialities. 



This is the essential and primary fact that com- 



[275] 



