Multiplication of Extremes 745 



selection-process. In practice it is of secondary 

 importance, and in nature it takes a very subor- 

 dinate position. For this reason it will be best 

 to confine further discussions to the experience 

 of the breeders. 



Two different ways are open to make fluctuat- 

 ing variability profitable. Both consist in the 

 multiplication of the chosen extremes, and this 

 increase may be attained in a vegetative man- 

 ner, or by the use of seeds. Asexual and sexual 

 propagation are different in many respects, and 

 so they are also in the domain of variability. 



In order to obtain a clear comprehension of 

 this difference, it is necessary to start from the 

 distinction between individual and partial fluc- 

 tuations, as given in the last lecture. This 

 distinction may be discussed more understand- 

 ingly if the causes of the variability are taken 

 into consideration. We have dealt with them 

 at some length, and are now aware that inner 

 conditions only, determine averages, while some 

 fluctuation around them is allowable, as influ- 

 enced by external conditions. These outward 

 influences act throughout life. At the very first 

 they impress their stamp on the whole organism, 

 and incite a lasting change in distinct directions. 

 This is the period of the development of the 

 germ within the seed ; it begins with the fusion 

 of the sexual cells, and each of them may be in- 



