HEREDITY 547 



ents and offspring, not only the complicated reduction 

 divisions involved in the formation of the gametes, but 

 also the nuclear and cell-fusions accomplished by the union 

 of the egg and sperm in fertilization. Both processes — 

 the formation of the gametes, and their fusion — offer 

 almost unlimited opportunities for alterations of the pro- 

 toplasm — especially that of the nucleus. This method of 

 reproduction, therefore, has the very greatest interest and 

 importance for the study of heredity. In the fertilized 

 egg^ are united the inheritances from two parents — from 

 two distinct lines of ancestry — protoplasms (germ-plasms) 

 with two entirely different histories extending back into 

 the past, no one knows how far. How will these two 

 inheritances affect each other when they intermingle in 

 the fertilized egg? Will one tend to inhibit or check cer- 

 tain characteristics or functions of the other; will they 

 evenly blend, so as to produce an expression intermediate 

 between that of the parents; or may entirely new sub- 

 stances be formed or new combinations take place, result- 

 ing in an entirely new expression in the offspring? 



467. Methods of Study. — To endeavor to answer the 

 questions just asked is as fascinating an occupation as it is 

 important, and the answers are significant for man, as well 

 as for plants. It is indeed, a fortunate thing that prin- 

 ciples ascertained by studying plants apply equally to man 

 and other animals, since plants are so much easier to 

 handle in experimental investigations. 



We may go about the answering of these questions in 

 either of two ways. We may gather large numbers of 

 statistics to measure and analyze {statistical or hiometrical 



* The fertilized egg (as Thomson has pointed out) is the inheritance, 

 and becomes, in the mature individual, the inheritor. 



