Yes, by Darwin himself.
“If my theory be true, numberless intermediate varieties, linking most closely all of the species of the same group together must assuredly have existed... Consequently, evidence of their former existence could be found only amongst fossil remains” (“The Origin of Species” by Charles Darwin, Chapter 6, “Difficulties of Theory”).
Scientific observation: Numberless intermediate varieties have NOT been found amongst fossil remains. In fact, the lack of intermediate transitional fossils has even been described as the “trademark secret of paleontologists” by famed evolutionists such as Dr. Stephen Gould.
Conclusion: Darwin’s theory is NOT true.