V. ATAVISM. 



§12. ATAVISM BY SEEDS AND BUDS. 



HoFMEiSTER ill liis AUgcuicbic Morphologic defines 

 atavism in these words: ''The occurrence of reversions, 

 the offspring of a variety of known origin resembhng 

 the parent type" (p. 559). 



According to the meaning of the word "known" in 

 the above definition the term atavism may embrace quite 

 a series of phenomena of the most diverse importance. 

 It may mean either that this origin must have been actu- 

 ally observed, or that it can be inferred with sufficient 

 certainty from comparative and systematic studies. If 

 we are merely dealing with morphological questions this 

 distinction may appear unessential, but as soon as our 

 object is to test by experiment the results obtained, it 

 becomes of the highest importance. For to obtain true 

 experimental proof of atavism it is obvious that the 

 origin of the forms should be known directly by observa- 

 tion. 



The origin of a whole series of varieties and ele- 

 mentary species from their parent forms, however, is 

 sufficiently established by the historical evidence relating 

 to their first appearance. It seems therefore feasible to 

 confine our attention to such cases and to draw a distinc- 

 tion between physiological and phylogenetic atavism. The 

 former is reversion to actually known ancestors, the latter 

 to systematic ancestors. 



