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Lecture IX 



CROSSES OF SPECIES AND VARIETIES 



In the foregoing lectures I have tried to show 

 that there is a real difference between element- 

 ary species and varieties. The first are of 

 equal rank, and together constitute the col- 

 lective or systematic species. The latter are 

 usually derived from real and still existing 

 types. Elementary species are in a sense inde- 

 pendent of each other, while varieties are of a 

 derivative nature. 



Furthermore I have tried to show that the 

 ways in which elementary or minor species must 

 have originated from their common ancestor 

 must be quite different from the mode of origin 

 of the varieties. We have assumed that the 

 first come into existence by the production of 

 something new, by the acquirement of a char- 

 acter hitherto unnoticed in the line of their an- 

 cestors. On the contrary, varieties, in most 

 cases, evidently owe their origin to the loss of 

 an already existing character, or in other less 

 frequent cases, to the re-assumption of a quality 



247 



