102 THE 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 mobility has been replaced by a certain quiescence, and 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 they 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, w^hereas the " bad species " are 

 susceptible of analysis, — the other alternative alone is 

 possible, that, as Haeckel says, if we knew them thg- 

 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 w^ith 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 



