CHAPTEE YIII. 



HEKEDITT. 



(5 80. Alkeady, in the last two chapters, tJie law of heredi- 

 tary transmission has heen tacitly assumed ; as, indeed, it 

 unavoidably is in all such discussions. Understood in its 

 entirety, the law is, that each plant or animal produces 

 others of like kind with itself : the likeness of kind consist- 

 ing, not so much in the repetition of individual traits, as in 

 the assumption of the same general structure. This truth has 

 been rendered so familiar by daily illustration, as almost to 

 have lost its significance. That wheat produces wheat — that 

 existing oxen have descended from ancestral oxen — that every 

 unfolding organism eventually takes the form of the class, 

 order, f^enus, and species from which it sprang ; is a fact 

 which, by force of repetition, has acquired in our minds 

 almost the aspect of a necessity. It is in this, however, 

 that Heredity is principally displayed : the phenomena com- 

 monly referred to it, being quite subordinate manifestations. 

 And, as thus understood, Heredity is universal. The various 

 instances of heterogenesis lately contemplated, seem, indeed, 

 to be at variance with this assertion. But they are not 

 really so. Though the recurrence of like forms, is, in these in- 

 stances, not direct but cyclical, still, the like forms do recur ; 

 and when taken together, the group of forms produced during 

 one of the cycles, is as much like the groups produced in pre- 

 ceding cycles, as the single individual arising by homo- 

 genesis, is like ancestral individuals. 



