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IMPEKFECTION OF THE 
Chap. IX. 
of any decided advantage, or when further modified and 
improved, they would slowly spread and supplant their 
parent-forms. When such varieties returned to their 
ancient homes, as they would differ from their former 
state, in a nearly uniform, though perhaps extremely 
slight degree, they would, according to the principles 
followed by many palaeontologists, be ranked as new and 
distinct species. 
If then, there be some degree of truth in these 
remarks, we have no right to expect to find in our 
geological formations, an infinite number of those fine 
transitional forms, which on my theory assuredly have 
connected all the past and present species of the same 
group into one long and branching chain of life. We 
ought only to look for a few Links, some more closely, 
some more distantly related to each other; and these 
links, let them be ever so close, if found in different 
stages of the same formation, would, by most palaeonto¬ 
logists, be ranked as distinct species. But I do not pre¬ 
tend that I should ever have suspected how poor a 
record of the mutations of life, the best preserved 
geological section presented, had not the difficulty of 
our not discovering innumerable transitional links be¬ 
tween the species which appeared at the commencement 
and close of each formation, pressed so hardly on my 
theory. 
On the sudden appearance of whole groups of Allied 
Species ,'—The abrupt manner in which whole groups of 
species suddenly appear in certain formations, has been 
m-ged by several palaeontologists—for instance, by 
Agassiz, Pictet, and by none more forcibly than by 
Professor Sedgwick—-as a fatal objection to the belief 
in the transmutation of species. If numerous species, 
belonging to the same genera or families, have really 
