Stability and Real Atavism 155 



which have been discussed in former chapters. 

 Their general character lies in their fidelity to 

 type, and in the fact that this is single, and not 

 double, as in the sporting varieties. 



But the current belief is, that they are only 

 true to their peculiarities to a certain degree, 

 and that from time to time, and not rarely, 

 they revert to the type from which they have 

 arisen. Such reversion is supposed to prove 

 that they are mere varieties, and at the same 

 time to indicate empirically the species from 

 which they have sprung. 



In the next lecture we shall examine critically 

 the evidence on which this assumption rests. 

 Before doing so however, it will be necessary 

 to collate the cases in which there is no re- 

 version at all, or in which the reversion is ab- 

 sent at least in experimental and pure sowings. 



In the present state of our knowledge it is 

 very difficult to decide, whether or not true re- 

 version occurs in constant varieties. If it does 

 occur, it surely does so very rarely and only 

 under unusual circumstances, or in particular 

 individuals. However when such individuals 

 are multiplied by buds and especially when they 

 are the only representatives of their variety, 

 the reversion, though theoretically rare, will be 

 shown by nearly every individual of the prog- 

 eny. Examples of this will be given below. 



