What forms of variability did Charles Darwin distinguish?

Specific variability, indefinite variability, individual differences, bud variation – such forms of variability were distinguished by the famous naturalist Charles Darwin.
Certain variability is variability that depends on certain conditions. For example: weight depends on the amount and quality of food that the animal eats; the appearance depends on the conditions and climate where the person lives for generations.
Uncertainty variability are minor features that may differ between individuals of the same species.
Individual differences are differences that appear in the offspring from the same parents, but have individual differences even though they belong to the same species. For example: an extra limb, an organ, a different color.