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.

可变性受许多复杂的规律支配， 受相关生长、 补偿、部件使用和停用的增加以及周围条件的明确作用影响。

A grand and almost untrodden field of inquiry will be opened, on the causes and laws of variation, on correlation, on the effects of use and disuse, on the direct action of external conditions, and so forth.

一个宏伟而几乎无人涉足的研究领域将被打开，涉及变异的原因和规律、相关性、使用和废弃的影响、外部条件的直接作用等等。