02 THE DOCTRINE OF DESCENT. 
less fettered by tradition and law than in the definition 
of species. The literature of ornithology during the last 
forty years could furnish thousands of the strangest 
examples of the Babel-like confusion which was thus 
introduced. 
There is no question that a great, perhaps the greater, 
number of organisms now existing are in a condition 
in which, according to their internal and external re- 
lations, they may be characterized by Natural History 
as so-called species, and for the purpose of recognition 
ard scientific treatment in general, must needs be so 
characterized. But this stability,as may be shown both 
directly and by analogy, is under all circumstances only 
temporary, and we have whole classes of organisms to 
which it is impossible, even with the widest reservations, 
to apply the old idea of species, with its immutability of 
essential characteristics. If weare able to furnish incon- 
trovertible proofs of the existence of such non-specific 
groups, the old system and the dogma of species are once 
for all set aside, and the positive basis of a new doctrine 
is secured, This evidence is supplied in two directions. 
Some classes of organisms in their present state vacillate 
and fluctuate in form, in such a manner that it is utterly 
impossibl]+ to fix the characteristics of species or genus, 
They are in an extreme grade of mutability, which, in 
others, has given way to an apparent state of repose. 
Other series of facts, exhibiting the most obvious muta- 
bility of species, are displayed by certain antediluvian 
groups in the succession of forms called “ species.” 
Even before the appearance of Darwin's work on the 
“Origin of Species,” Carpenter, in the course of his 
rescarches on the Foraminifera, arrived at the con- 
