HEREDITY, AND THE ORIGIN OF SPECIES. 7 
Of the many other phases of the existence, and distribu- 
tion of organisms, that have been considered in a contro- 
versial way to prove this, or that, hypothesis it must be 
ceded that in this discussion of the effect of isolation upon 
the origin and preservation of forms, the evidence ad- 
duced, so far as plants are concerned does not especially 
favor any of the suppositions discussed previously. In 
like manner the bogie of the effects of close- and cross- 
breeding is used in the most reckless manner to support the 
most diverse generalizations. Until investigated with the 
exactness demanded by modern technique, and by the most 
approved methods with material of undoubted pedigree, 
we may well consider close- and cross-fertilization as ope- 
rations the value of which is yet to be estimated. Nearly 
all of the available data have been obtained with domesti- 
cated races, artificially selected from what, in the natural 
conditions, may be the most extreme phase of a character, 
and far from the norm of the species in many particulars. 
The retrogression toward this norm may be a deterioration 
of the economic value of the strain, yet from the point of 
view of the species itself it may be a direct movement 
toward the average condition, in which we may not secure 
so much speed, beef, wool, milk, grain, or fibre, as in strains 
bred and selected for these features. 
It is with great relief that we turn from these historical 
and hypothetical considerations to the authenticated facts, 
the interpretation of which affords some positive generali- 
zations as to phylogenetic procedure. In other words we 
take up the observations by which species have arisen, in 
place of the suppositions as to how they may have arisen. 
First, it has been known for over half a century that 
fixed forms, constant in inheritance and self-maintenant, 
therefore constituting species have resulted from hybridi- 
zation. The fertilization of the egg-cell of one species by 
the pollen of another, often results in an interlocked and 
