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sary to suppose that we are ignorant of the first appearance of 
all those specific and generic types which make their appear- 
ance suddenly in the stratified series. In other words we must 
suppose that fully three-fourths of all the known species of 
fossils had been in existence an indefinite period before their 
first appearance in the rocks as known to us. I apprehend that 
every evolutionist will admit this, since the cases in which it 
can actually be shown that a fossil species came into existence 
“ coincident, both in space and time, with a pre-existing closely- 
allied species,” are, on the most liberal estimate, not more than 
one-fourth of the total number of those with which we are 
already acquainted. All the other species, of which this can- 
not be shown, must, in accordance with the above dictum , have 
been in existence prior to the period where they now first 
appear upon the scene. 
The types of species and genera, to say nothing of those of fami- 
lies and orders, which make their appearance in the Cambrian 
period, are so numerous that we are compelled by this argu- 
ment to assume that they themselves must have been in exist- 
ence for an indefinitely long period before the commencement 
of the Cambrian ; whilst the types from which they were de- 
rived must have flourished in ages so immeasurably earlier that 
the very imagination is left powerless. Indubitably, there is 
every reason to believe that the great pile of Laurentian 
sediments was once fossiliferous, and that the Laurentian 
period was anything but “ azoic.” Upon strict Darwinian 
principles, however, the Laurentian period, long as it must 
have been, is altogether inadequate for the development of all 
the forms of life which make their first nominal appearance 
in the Cambrian. We are, therefore, compelled to assume the 
former existence of vast Pre-Laurentian deposits, the memorials 
of an ancient period rich in life, which must have been de- 
stroyed by subsequent denudation. No one dare assert that 
such deposits may not have existed ; but as we have absolutely 
no proof of such a thing, their character and contents can 
hardly be brought forward as factors in a scientific argument. 
Mr. Darwin, therefore, candidly admits that “the case at pre- 
sent must remain inexplicable.” 
In the case which we have been considering, the argument 
employed by Mr. Darwin, though not demanding such extensive 
hypotheses, is equally incapable of proof, and must, in my 
opinion, be equally rejected. We find, for example, in the 
Devonian rocks of North America, amongst many others, the 
entirely new Brachiopodous type, Productella, represented by 
twenty-one known species, all, of course, equally new. Upon 
