[247]
LECTURE IX
CROSSES OF SPECIES AND VARIETIES
In the foregoing lectures I have tried to show that there is a real
difference between elementary species and varieties. The first are of
equal rank, and together constitute the collective or systematic
species. The latter are usually derived from real and still existing
types. Elementary species are in a sense independent 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 character hitherto unnoticed in
the line of their ancestors. 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 [248]
formerly lost. Some may originate in a negative, others in a positive
manner, but in both cases nothing really new is acquired.
This distinction holds good for all cases in which the relationship
between the forms in question is well known. It seems entirely
justifiable therefore to apply it also to cases in which the systematic
affinity is doubtful, as well as to instances in which it is impossible
to arrive at any taxonomic conclusions.
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