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these last cannot be held to be less perfect than those with the medium 
numbers. Further^ as Barrande well shows, on the principle of survival of 
the fittest, the species with the medium number of joints are best fitted for 
the struggle of existence. But in that case the primordial Trilobites made a 
great mistake in passing at once from the few to the many-segmented stage, 
or vice versa , and omitting the really profitable condition which lay between. 
In subsequent times they were thus obliged to undergo a retrograde evolution, 
in order to repair the error caused by the want of foresight or by the precipi- 
tation of their earlier days. But, like other cases of late repentance, theirs 
seems not to have quite repaired the evils incurred ; for it was after they 
had fully attained the golden mean that they failed in the struggle, and 
finally became extinct. “ Thus the infallibility which these theories attribute 
to all the acts of matter organizing itself is gravely compromised,” and this 
attribute would appear not to reside in the trilobed tail, any more than, 
according to some, in the triple crown. 
In the same manner the palaeontologist of Bohemia passes in review all 
the parts of the Trilobites, the succession of their species and genera in 
time, the parallel between them and the Cephalopods, and the relations of 
all this to the primordial fauna generally. Everywhere he meets with the 
same result ; namely, that the appearance of new forms is sudden and 
unaccountable, and that there is no indication of a regular progression by 
derivation. He closes with the following somewhat satirical comparison, of 
which I give a free translation: — “In the case of the planet Neptune it 
appears that the theory of astronomy was wonderfully borne out by the 
actual facts as observed. This theory, therefore, is in harmony with the 
reality. On the contrary, we have seen that observation flatly contradicts 
all the indications of the theories of derivation with reference to the 
composition and first phases of the primordial fauna. In truth, the special 
study of each of the zoological elements of that fauna has shown that the 
anticipations of the theory are in complete discordance with the observed 
facts. These discordances are so complete and so marked that it almost 
seems as if they had been contrived on purpose to contradict all that these 
theories teach of the first appearance and primitive evolution of the forms of 
animal life.” 
This testimony is the more valuable, inasmuch as the annulose animals 
generally, and the Trilobites in particular, have recently been a favourite 
field for the speculations of our English evolutionists. The usual argu- 
mentum ad ignorantiam. deduced from the imperfection of the geological 
record, will not avail against the facts cited by Barrande, unless it could be 
proved that we know the Trilobites only in the last stages of their decadence, 
and that they existed as long before the Primordial as this is before the 
Permian. Even this supposition extravagant as it appears, would by no 
means remove all the difficulties. 
