This may be attributed partly to the principle of correlated growth, and partly to so-called spontaneous variation.

这可能部分归因于相关增长的原则， 部分归因于所谓的自发变异。

We shall thus be enabled to see the part which habit and the selection of so-called spontaneous variations have played in modifying the mental qualities of our domestic animals.

因此，我们将能够看到习惯和所谓的自发变异的选择在改变我们家畜的心理素质方面所起的作用。

For all spontaneous variations in the right direction will thus be preserved; as will those individuals which inherit in the highest degree the effects of the increased and beneficial use of any part.

因为在正确方向上的所有自发变化都将因此得以保存；那些在最大程度上继承了任何部分的增加和有益使用的影响的个人也是如此。

In the third place, we have to allow for the direct and definite action of changed conditions of life, and for so-called spontaneous variations, in which the nature of the conditions apparently plays a quite subordinate part.

第三， 我们必须考虑到变化的生活条件的直接和明确的作用，以及所谓的自发变化， 其中条件的性质显然起着相当次要的作用。