Seite - 506 - in The Origin of Species

506 ORIGIN OF SPECIES manner. We clearly see this in the fossil remains from con- secutive formations invariably being much more closely re- lated to each other, than are the fossils from widely separated formations. Such is the sum of the several chief objections and diffi- culties which may be justly urged against the theory; and I have now briefly recapitulated the answers and explanations which, as far as I can see, may be given. I have felt these difficulties far too heavily during many years to doubt their weight. But it deserves especial notice that the more im- portant objections relate to questions on which we are con- fessedly ignorant; nor do we know how ignorant we are. We do not know all the possible transitional gradations be- tween the simplest and the most perfect organs ; it cannot be pretended that we know all the varied means of Distribution during the long lapse of years, or that we know how imper- fect is the Geological Record. Serious as these several ob- jections are, in my judgment they are by nomeans sufficient to overthrow the theory of descent with subsequent modification. Now let us turn to the other side of the argument. Under domestication we see much variability, caused, or at least excited, by changed conditions of life ; but often in so obscure a manner, that we are tempted to consider the variations as spontaneous. Variability is governed by many complex laws, —by correlated growth, compensation, the increased use and disuse of parts, and the definite action of the surrounding conditions. There is much difficulty in ascertaining how largely our domestic productions have been modified; but we may safely infer that the amount has been large, and that modification can be inherited for long periods. As long as the conditions of life remain the same, we have reason to believe that a modification, which has already been inherited for many generations, may continue to be inherited for an almost infinite number of generations. On the other hand, we have evidence that variability when it has once come into play, does not cease under domestication for a very long period ; nor do we know that it ever ceases, for new varieties are still occasionally produced by our oldest domesticated productions.