Why didn't darwin use mendel's results when formulating his theory of evolution by natural selection?

Answer;

Mendel's work was not well known until many years after Darwin published his theory of evolution

Explanation;

-Mendel's work was ignored because it was not widely distributed, and he didn't make an effort to promote himself. In actual fact, the reasons are more complex.

-Gregor Mendel had the answer to Darwin's problem. Traits were not blended, but inherited whole. And according to Mendel's laws of inheritance, a trait that might disappear in one generation might reappear in the following generation. Modern Neo-Darwinism combines both Darwin's and Mendel's work.