SCOPE OF GENETICS 



Now obviously the diversity of form which 

 is characteristic of the animal and plant world 

 must be somehow represented in the gametes, 

 since it is they which bring into each organism 

 all that it contains. I am aware that there is 

 interplay between the organism and the cir- 

 cumstances in which it grows up, and that 

 opportunity given may bring out a potenti- 

 ality which without that opportunity must 

 have lain dormant. But while noting paren- 

 thetically that this question of opportunity 

 has an importance, which some day it may be 

 convenient to estimate, the one certain fact is 

 that all the powers, physical and mental that 

 a living creature possesses were contributed 

 by one or by both of the two germ-cells which 

 united in fertilisation to give it existence. 

 The fact that two cells are concerned in the 

 production of all the ordinary forms of life 

 was discovered a lon^ while a^o, and has 



