of characters lost long ago by variation; and it is hardly applicable to races
or species which, after having been crossed at some former period with a
distinct form, and having since lost all traces of the cross, nevertheless
occasionally yield an individual which reverts (as in the case of the great-
great-grandchild of the pointer Sappho) to the crossing form. The most simple
case of reversion, namely, of a hybrid or mongrel to its grandparents, is
connected by an almost perfect series with the extreme case of a purely-bred
race recovering characters which had been lost during many ages; and we are
thus led to infer that all the cases must be related by some common bond.

Gartner believed that only highly sterile hybrid plants exhibit any tendency
to reversion to their parent-forms. This erroneous belief may perhaps be
accounted for by the nature of the genera crossed by him, for he admits that
the tendency differs in different genera. The statement is also directly
contradicted by Naudin's observations, and by the notorious fact that
perfectly fertile mongrels exhibit the tendency in a high degree,--even in a
higher degree, according to Gartner himself, than hybrids. (13/51.
'Bastarderzeugung' s. 582, 438, etc.)

Gartner further states that reversions rarely occur with hybrid plants raised
from species which have not been cultivated, whilst, with those which have
been long cultivated, they are of frequent occurrence. This conclusion
explains a curious discrepancy: Max Wichura (13/52. 'Die Bastardbefruchtung...
der Weiden' 1865 s. 23. For Gartner's remarks on this head, see
'Bastarderzeugung' s. 474, 582.) who worked exclusively on willows which had
not been subjected to culture, never saw an instance of reversion; and he goes
so far as to suspect that the careful Gartner had not sufficiently protected
his hybrids from the pollen of the parent-species: Naudin, on the other hand,
who chiefly experimented on cucurbitaceous and other cultivated plants,
insists more strenuously than any other author on the tendency to reversion in