Origin of Species and Varieties 579 



been met with. Even in this case only some- 

 thing would be discovered about the time of the 

 change, but nothing about its real nature. 



So it is in many cases. If a variety is ob- 

 served in a number of specimens at the time 

 of its first discovery, and at a locality not 

 studied previously, it takes the aspect of an old 

 form of limited distribution, and little can be 

 learned as to the circumstances under which it 

 arose. If on the contrary it occurs in very 

 small numbers or perhaps even in a single in- 

 dividual, and if the spot where it is found is 

 located so that it could hardly have escaped pre- 

 vious observation, then the presumption of a re- 

 cent origin seems justified. 



What has to be ascertained on such occasions 

 to give them scientific value? Three points 

 strike me as being of the highest importance. 

 First, the constancy of the new type; secondly, 

 the occurrence or lack of intermediates, and last, 

 but not least, the direct observation of a re- 

 peated production. 



The first two points are easily ascertained. 

 Whether the new type is linked with its more 

 common supposed ancestor by intermediate 

 steps is a query which at once strikes the bota- 

 nist. It is commonly recorded in such cases, and 

 we may state at once that the general result is, 

 that such intermediates do not occur. This is 



