Heredity and Natural Selection. 311 



of my Yiew of the nature of heredity enables us to 

 avoid both of these results, since it shows that special 

 homologies may be due to heredity of one sort, and general 

 homologies to heredity of another sort. Since correspond- 

 ing cells in the homologous parts of the body of any indi- 

 yidual are derived from closely related parts of the Q%g, 

 they may be affected by similar gemmules and may thus 

 give rise to what Darwin calls analogous variations. 

 This form of inheritance I propose to call ontogenetic 

 heredity, to distinguish it from ordinary inheritance 

 from an ancestor. I shall point out, in anothei* jilace, 

 that while special homologies are due to ordinary or 

 phytogenetic heredity, that is, to descent from a com- 

 mon ancestor, general homologies are, in many cases, due 

 to ontogenetic heredity ; that special homologies are old, 

 and that they indicate genetic relationship, and thus 

 enable us to trace the origin and history of animals, 

 while general homologies are, in many cases, new, and 

 recently acquired by secondary modification, and they 

 do not indicate ancestry. 



