1884.] 
between Races and other Species. 41 1 
].t has often been doubted whether permanent species can 
aiise from hybrids. Hybrids between species mutually re- 
mote from each other are often sparingly fruitful. But we 
often find, e.g ., in R. ccesius and R. tomentosus, in favourable 
localities, all intermediate links between sterile and fairly 
fruitful specimens. Observation further shows that with 
time fruitful races can originate from hybrids of sparing 
fertility. The original lack of permanence in hybrids, as 
numerous observations prove, loses itself often entirely in 
successive generations. Many examples are also known 
where hybrids artificially produced agree exactly with natu- 
rally occurring “good species.” Some of the sparingly 
fruitful hybrids obtained by Herr Focke by sowing the 
fruits of R. ccesius and R. idceus cannot be distinguished from 
the Swedish species, R. pruinus, and the Pomeranian R. 
maximus. Ihe locally distributed blackberries are certainly 
in great part mixtures of races growing in the same district. 
On the other hand, it is certain that many species and races 
with mixed heterogeneous pollen cannot be descended from 
hybrids of known living forms. To be consistent we must 
still assume that these are also hybrid forms, but that their 
origin extends far back, — in case of R. fruticosus, e.g., as far 
as the Tertiary epoch. On the other hand, the species with 
homogeneous pollen may be regarded as of unmixed origin. 
From the circumstance that the Rubus seeds are often 
carried about by animals, and from their great adaptability, 
a local mixture of species will easily have occurred, even 
though under certain circumstances the immigrant forms 
may have been subsequently displaced by their competitors. 
In the struggle for existence vitality and adaptability 
generally determine the result. Since in this respeCt, as 
Darwin has shown, individuals of mixed origin are generally 
better off than their parents, it is not merely conceivable, 
but even probable, that hybrid races may survive their 
ancestry. The disadvantage of a heterogeneous granulation 
of the pollen is comparatively of little weight. 
If we now consider that the majority of our cultivated 
plants have been produced by crossing, whilst all our art 
and all the exaggerated influences of soil and climate have 
not been able to effect much change in given natural species, 
we shall not be able to resist the conviction that the crossing 
of species and races has a greater effect in the formation of 
new species than has been hitherto credited. The prejudice 
which uncritically ascribes all creative influence to the soil 
and the climate alone must be overcome. 
In order that mixtures may spring up in Nature decided 
2 e 2 
