Principles of Heredity 199 



offspring, though pure and stable varieties that have 

 exhibited the same characters in a high degree for 

 generations have not that power. As we now know, the 

 presence or absence of a character in a progenitor may be 

 no indication whatever as to the probable presence of the 

 character in the offspring ; for the characters of the latter 

 depend on gametic and not on zygotic differentiation. 



The problem is of a different order of complexity from 

 that which Professor Weldon suggests, and facts like these 

 justify the affirmation that if we could at this moment 

 bring together the whole series of individuals forming the 

 pedigree of Telephone, or of any other plant or animal 

 known to be aberrant as regards heredity, we should have 

 no more knowledge of the nature of these aberrations ; no 

 more prescience of the moment at which they would begin, 

 or of their probable modes of manifestation ; no more 

 criterion in fact as to the behaviour such an individual 

 would exhibit in crossing*, or solid ground from which to 

 forecast its posterity, than we have already. We should 

 learn then what we know already that at some parti- 

 cular point of time its peculiar constitution was created, 

 and that its peculiar properties then manifested themselves : 

 how or why this came about, we should no more compre- 

 hend with the full ancestral series before us, than we can 

 in ignorance of the ancestry. Some cross-breds follow 

 Mendelian segregation ; others do not. In some, palpable 

 dominance appears ; in others it is absent. 



If there were no ancestry, there would be no posterity. 

 But to answer the question why certain of the posterity 

 depart from the rule which others follow, we must know, 

 not the ancestry, but how it came about either that at a 



* Beyond an indication as to the homogeneity or "purity" of its 

 gametes at a given time. 



