60 The Different Modes of Origin of new Species. 
But the large number of cases of forms preliminarily 
described as varieties but which possibly may be only 
variants, is one of the most considerable obstacles in this 
inquiry. 
LINNAEUS himself followed two distinct rules in sub- 
dividing his species. According to the one the species 
was regarded as the type from which the varieties were 
derived ; according to the other, however, the species was 
regarded as a collective group which embraced a certain 
number of units of equal value. The separation is sharp 
and definite and LINNAEUS was obviously perfectly con- 
scious of its reality. In the derived varieties the series 
begins with /? followed by y, 3, e etc. ; it is taken for 
granted that the type or Forma geniiina represents the a. 
In a homonomous series there is no such Forma gcnuina, 
and the series of varieties therefore begins with a. 
Let us consider the two cases separately and let us 
begin with the second. 
LINNAEUS'S homonomous varieties, a, /?, y etc., are 
sometimes arranged in groups, and sometimes not (as in 
Teucrium Poliiiin, Lavandula Spica, etc.). In the former 
case the species falls into two or several subspecies, each 
of which again may include one or several varieties. For 
instance Euphorbia e.rigua has two subspecies acuta and 
retusa, the first of which consists of one and the second 
of two varieties. Beta mdgaris has the well-known sub- 
species mbra and Cicla; the first of these embraces five, 
the second two varieties. In these species there is no 
Forma typica or Forma gcnuina. The variety which is 
named first has no other priority over the others. 
In such cases the species is a group of similar com- 
position to that of a genus and of a family ; since in these 
no particular species or genus is regarded as the proto- 
