On atavism the Machine can have no mercy.

对于返祖现象，大机器有所怜悯的。

The atavism passed and he walked the room still, stopping from time to time to look at the telegram.

返祖现象过去了， 他仍然在房里走着， 时停下来看看电报。

In other words, metamorphosis in mole salamanders is an atavism.

换句话说，螈的变形就是返祖。

If for any reason this does not happen, the ancestral feature may not disappear, leading to an atavism.

如果因为某个原因这种现象没有发生，这种祖先的特征就可能消失，产生返祖。