Vv. VARIETIES, ETC. A3 
revert into the type-species. But when they come to practice, it 
is found that they too often cannot at all agree among themselves 
where to trace the dividing line between the two categories. And 
we are at last practically left in this alternating definition :— 
Species are wider varieties ; varieties are closer species. 
Much new light has been brought upon this debatable matter 
by the theory of Charles Darwin, so rapidly become known to all 
naturalists, and still so much discussed among them, although 
with an increasing tendency to acceptance. It bears very im- 
portantly on phyto-geography in various ways; and thus some 
consideration of that theory has become unavoidable with every 
student in this department of botany. According to the Darwinian 
theory, there is no absolute difference between species and varieties. 
They are supposed to be the same in kind, differing only in age or 
degree. A slight variety is held to be an “incipient species,” the 
progeny of which, in course of many generations, and by increasing 
variation, may eventuate in a new and (so considered) distinct 
species. Mr. Darwin's idea is, that organic life on the earth com- 
menced with extremely few original forms, possibly with one only ; 
all the thousands on thousands of present species, and all the 
countless numbers (millions on millions?) of extinct species, 
having proceeded from those few original forms. He does not 
insist upon this origin of all from one only; but he writes, “I be- 
lieve that animals have descended from at most only four or five 
progenitors, and plants from an equal or lesser number.” (Edition 
2, p- 518). The process by which those few original forms have 
become the million or so of species which now exist, is alleged to 
have been of a two-fold character, — accumulation of divergent 
variations by “‘ Natural Selection.” 
First, as to accumulating divergences or variations. The imme- 
diate progeny usually resemble their parents, without being always 
exact repetitions of those parents, or exactly like each other. Any 
little difference apparent in the progeny is so far a divergence 
from the characters of their parents; and they thus become two 
varieties, or a normal and a varied form. The progeny become 
