The rule applies very strongly in the case of secondary sexual characters, when displayed in any unusual manner.

当以任何不寻常的方式显示时， 该规则非常适用于第二性征的情况。

I think it will be admitted by naturalists, without my entering on details, that secondary sexual characters are highly variable.

我认为博物学家会承认第二性征是高度可变的， 而无需我详细说明。

Secondary sexual characters are highly variable, and such characters differ much in the species of the same group.

第二性征是高度可变的，并且这种性征在同一群体的物种中差异很大。

The rule applies to males and females; but more rarely to females, as they seldom offer remarkable secondary sexual characters.

该规则适用于男性和女性； 但对女性来说更少， 因为她们很少提供显着的第二性征。

The term, secondary sexual characters, used by Hunter, relates to characters which are attached to one sex, but are not directly connected with the act of reproduction.

亨特使用的术语“第二性征” 与附属于一种性别但与繁殖行为没有直接联系的特征有关。

The rule being so plainly applicable in the case of secondary sexual characters, may be due to the great variability of these characters, whether or not displayed in any unusual manner—of which fact I think there can be little doubt.

这条规则如此明显地适用于第二性征， 可能是由于这些性格的巨大可变性，无论是否以任何不寻常的方式表现出来——我认为这一事实是毋庸置疑的。