SOME NEW PRINCIPLES 243 



marised in the statement that whilst the old-fashioned 

 breeder looked for guidance to the pedigree of the 

 animals and plants he was breeding, the modern 

 one looks to their gametes ; the former looks to 

 their ancestry, and the latter to their offspring ; 

 the former looks backwards, the latter forwards. A 

 criticism which may be made of the modern metJiod 

 is that it amounts to nothing more than predicting 

 what will happen by finding out what does happen. 

 But this is not, in fact, a fair criticism. In the antithesis 

 in the last paragraph ancestry was opposed to off- 

 spring and not to posterity — to one generation only 

 and not to many. The breeder, according to the 

 old principles, required a knowledge of the parents 

 and of as many of the ancestors as possible, and 

 based his prediction on this knowledge without going 

 beyond it. The breeder, according to the new prin- 

 ciples, only requires a knowledge of the offspring, 

 and he only needs this as an indication of the germinal 

 contents of their parents ; he does go beyond the 

 characters of the offspring to the germinal contents 

 of their parents, and bases his prediction on this, 

 and not on the characters themselves. 



We have now to deal with another part of the 

 Mendelian doctrine, and with its application to 

 practice. This is the idea that the organism is 

 built up of independently heritable unit-characters. 

 I do not propose to consider here the question how 

 far it is likely that this conception will be found to 

 be applicable to all the characteristics of organisms. 

 That is a question to which, it seems to me, it is not 



