It will obviously thus act far more efficiently with those animals which unite for each birth; but, as already stated, we have reason to believe that occasional intercrosses take place with all animals and plants.

因此，它显然会更有效地处理那些每次出生都结合在一起的动物； 但是，如前所述，我们有理由相信所有动物和植物偶尔会发生杂交。