142 REV. JOHN GERARD, F.L.S., ON SPECIES AND THEIR ORIGIN. 
from them. Sterility or fertility in breeding would seem to be after 
all the true criterion for distinguishing between “species” and 
“varieties”; but this requires the patient following of the experi- 
mental method to check opinions formed from mere observation. 
Mr. Gerard quotes Huxley “ junior” and Huxley “senior,” as incon- 
sistent. Obviously the latter must correct the former. 
As research advanees, the Darwinian creed is apt to receive some 
rude shocks. Thus Mr. Gerard (pp. 129, 130) quotes Darwin himself 
as saying that the same identical species cannot be produced twice 
over, “even if the very same conditions of life, organic and inorganic, 
should recur.” That dogmatic utterance seems to have been rudely 
traversed of late by the reproduction of the Pleistocene species of 
small slender-limbed species of horse, which Professor Cossar Ewart, 
F.R.S., of Edinburgh, but named Equus agilis, but which Owen had 
described from a few fragments from the Oreston cavern as Asinus 
Jossilis, Professor Ewart, it would seem, has, in his experimental 
farm at Penicuik, reproduced, by the cross-breeding of some seven 
breeds of small horses, the identical species of horse which ranged in 
Pleistocene times from Algiers to the South of England; and he 
seems satisfied that it represents more than a mere “ variety,” but 
rather the “small slender-limbed species hunted and sketched or 
sculptured by our Paleolithic ancestors.” (See Nature, Jan. 20th, 
1910.) 
Ewart enumerates as specific characters—“a fine head, slender 
limbs and small hoofs, a mane which, instead of clinging to the 
neck, arches to one side, a well set-on tail, and only two out of the 
eight callosities usually found in horses; i.e, the four ergots and 
the hind chestnuts are absent.” Here again it remains for the 
naturalists to decide how far these amount to specific, as distinguished 
from varietal differentiac. Whatever uncertainty may beset this 
question, we may with a fair degree of certainty maintain, 1 think, 
that Professor Ewart’s results have given a practical demonstration 
to the important principle of “directivity,” as a necessary supple- 
ment to the crude Darwinian dogma of “natural selection by the 
survival merely of the fittest.” And in further illustration of this 
in the plant-world, we hear of a new “species” (? variety) of wheat 
obtained from cross-fertilisation of species or varieties of Triticum, 
and remarkable for its disease-resisting powers. 
Reply by the Rey. J. Gerarp, F.L.S.—I find the result of this 
