Natura non facit saltum

Natura non facit saltum, ita nec lex. Nature makes no leap, nor does the law. Co. Litt. 238.

References in classic literature ?
Difficulties on the theory of descent with modification -- Transitions -- Absence or rarity of transitional varieties -- Transitions in habits of life -- Diversified habits in the same species -- Species with habits widely different from those of their allies -- Organs of extreme perfection -- Means of transition -- Cases of difficulty -- Natura non facit saltum -- Organs of small importance -- Organs not in all cases absolutely perfect -- The law of Unity of Type and of the Conditions of Existence embraced by the theory of Natural Selection.