On this doctrine of the extermination of an infinitude of connecting links, between the living and extinct inhabitants of the world, and at each successive period between the extinct and still older species, why is not every geological formation charged with such links?  Why does not every collection of fossil remains afford plain evidence of the gradation and mutation of the forms of life?  We meet with no such evidence, and this is the most obvious and forcible of the many objections which may be urged against my theory.  Why, again, do whole groups of allied species appear, though certainly they often falsely appear, to have come in suddenly on the several geological stages?  Why do we not find great piles of strata beneath the Silurian system, stored with the remains of the progenitors of the Silurian groups of fossils?  For certainly on my theory such strata must somewhere have been deposited at these ancient and utterly unknown epochs in the world’s history.

I can answer these questions and grave objections only on the supposition that the geological record is far more imperfect than most geologists believe.  It cannot be objected that there has not been time sufficient for any amount of organic change; for the lapse of time has been so great as to be utterly inappreciable by the human intellect.  The number of specimens in all our museums is absolutely as nothing compared with the countless generations of countless species which certainly have existed.  We should not be able to recognise a species as the parent of any one or more species if we were to examine them ever so closely, unless we likewise possessed many of the intermediate links between their past or parent and present states; and these many links we could hardly ever expect to discover, owing to the imperfection of the geological record.  Numerous existing doubtful forms could be named which are probably varieties; but who will pretend that in future ages so many fossil links will be discovered, that naturalists will be able to decide, on the common view, whether or not these doubtful forms are varieties?  As long as most of the links between any two species are unknown, if any one link or intermediate variety be discovered, it will simply be classed as another and distinct species.  Only a small portion of the world has been geologically explored.  Only organic beings of certain classes can be preserved in a fossil condition, at least in any great number.  Widely ranging species vary most, and varieties are often at first local,—­both causes rendering the discovery of intermediate links less likely.  Local varieties will not spread into other and distant regions until they are considerably modified and improved; and when they do spread, if discovered in a geological formation, they will appear as if suddenly created there, and will be simply classed as new species.  Most formations have been intermittent in their accumulation; and their duration, I am inclined to believe, has been shorter than the average duration