On the "doubtful & obscure" subject of marriage of cousins, CD believes, that judging from the analogy of animals, no direct evil would follow from their marriage. He would, however, expect the offspring of unrelated parents to be somewhat superior in size and vigour. The injury from the increase of any bad tendency common to the family seems to CD more to be feared than mere consanguinity; "the good effects of crossing distinct families I look at as great & undoubted".