Origin of Species Variorum

variability in the offspring in both cases is notorious; but some few instances of both hybrids and mongrels long retaining a uniform character could be given. The variability, however, in the successive generations of mongrels is, perhaps, greater than in hybrids.

This greater variability in mongrels than in hybrids does not seem .. at all surprising. For the parents of mongrels are varieties, and mostly domestic varieties (very few experiments having been tried on natural varieties), and this implies ... that there has been recent variability, which would often continue and be added to that arising from the .. act of crossing. The slight variability of hybrids in .. the first ... generation, in contrast with ... the succeeding generations, is a curious fact and deserves attention. For it bears on .. the view which I have taken of one of the causes of ordinary variability: namely, that ... the reproductive system from being eminently sensitive to .. changed .. conditions of life, fails under these circumstances to perform its proper function of producing offspring identical in all respects with the parent-form. Now hybrids in the first generation are descended from species (excluding those .. long-cultivated) which have not had their reproductive systems in any way affected, and they are not variable; but hybrids themselves have their reproductive systems seriously affected, and their descendants are highly variable.

But to return to our comparison of mongrels and hybrids: Gärtner states that mongrels are more liable than hybrids to revert to either parent-form; but this, if it be true, is certainly only a difference in degree. Moreover, Gärtner expressly states that hybrids from long-cultivated plants are more subject to reversion than hybrids from species in their natural state; and this probably explains the singular difference in the results