Why then is not every geological formation and every stratum full of such intermediate links?

那么为什么不是每一个地质构造和每一个地层都充满了这样的中间环节呢？

So that the number of intermediate and transitional links, between all living and extinct species, must have been inconceivably great.

因此，所有现存物种和灭绝物种之间的中间和过渡环节的数量一定多得令人难以置信。

The main cause, however, of innumerable intermediate links not now occurring everywhere throughout nature depends, on the very process of natural selection, through which new varieties continually take the places of and supplant their parent-forms.

然而，现在自然界中并非到处都存在的无数中间环节的主要原因取决于自然选择的过程，通过这个过程， 新变种不断地取代和取代它们的亲本形式。

It is just possible, by the theory, that one of two living forms might have descended from the other; for instance, a horse from a tapir; and in this case DIRECT intermediate links will have existed between them.

从理论上讲， 两种生物中的一种可能是另一种的后代。例如，貘的马； 在这种情况下， 它们之间将存在 DIRECT 中间链接。