HALF RACES 149 
best developed as a rule either shows the racial char- 
acter in about half of the seedlings produced, or else 
exhibits in the great majority of its members a com- 
bination of the character of the species with that of 
the race. As an example, we may take the case of 
variegated plants, in which the leaves show streaks 
or patches of a yellow colour owing to the want of 
development of the proper green tint. An ordinary 
variegated plant, then, is looked upon as showing a 
combination of the green type with the yellow char- 
acter of a completely modified race—the aurea variety, 
although the latter exists as such only in a few rare 
cases, in which the plants bear leaves showing no 
green pigment at all. On the other hand, many 
species of plants produce a small proportion of varie- 
gated individuals at each sowing, as is often the case, 
for example, with Indian corn ; and this circumstance, 
according to de Vries, indicates the existence of the 
corresponding half-race. 
The relative development of the two coexisting 
characters in such cases is highly variable, as anyone 
may observe for himself in variegated grasses and 
similar plants. 
It might be supposed that it would be possible to 
pass from the species to the half-race, thence to the 
mid-race, and so on to the complete race simply by 
selection. De Vries shows that this is very rarely, if 
ever, the case. He regards the passage from a half- 
race to a mid-race, for example, as a mutation, and his 
observations seem to show that this transition is not 
more frequent than any other mutations. 
