[02 TIIE DOCTRINE OF DESCENT. 
inexplicable foundation, on a mystery, ought to be pro- 
scribed from science for evermore.” 
Without owning allegiance to any theory whatever, 
we are constrained to recognize the fact, that in various 
groups of organisms there even now exists such an 
instability of form, and such a degree of variability, 
that it is patent how constrained and artificial is their 
systematic separation. In many other groups, in most 
orders of the Mammalia, for example, this phase of 
mobility has been replaced by a certain quiescence, and 
the forms now presenting themselves for observation 
and comparison are so well defined from one another, 
that any fit into the system without difficulty as “good 
species.” But if the “ good species” are to be judged 
by the experiences made in regard to the “bad” ones, 
and if the preposterous hypothesis is not laid hold of, in 
contravention to all healthy human understanding, that 
“good species” originated in a miraculous manner inac- 
cessible to our cognition, whereas the “bad species” are 
susceptible of analysis,—the other alternative alone is 
possible, that, as Haeckel says, if we knew them tho- 
roughly, all species without exception would, in the sense 
of the species-makers, be “bad species.” We are also 
acquainted with a sufficient number of bad species to be 
capable of inferring the general law with certainty. 
Nevertheless, all further corroboration and discovery of 
bad species is acceptable. Regarded formerly by the 
systematists only as incumbrances and as stones rejected 
by the builders, they have now become the corner-stones 
of science. 
Is species therefore, we again inquire, to be entirely 
abandoned? Not so, for several reasons. Even assuming 
