His theory has been criticized and IMO he was walking it back in what you quoted.
Ernst Mayr, who some consider the current dean of evolution said, "Wherever we look at the living biota...discontinuities are overwhelming frequent...The discontinuities are even more striking in the fossil record. New species usually appear in the fossil record suddenly, not connected with their ancestors by a series of intermediates in his book, "What evolution is," p.189. He also said the fossil record is woefully inadequate, p.89.
If evolution was true the great majority of fossils would be intermediates, and today you have none.
He also said this:
"Paleontologists have paid an enormous price for Darwin's argument. We fancy ourselves as the only true students of life's history, yet to preserve our favored account of evolution by natural selection we view our data as so bad that we almost never see the very process we profess to study. ...The history of most fossil species includes tow [sic] features particularly inconsistent with gradualism: 1. Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change I [sic] usually limited and directionless. 2. Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and 'fully formed.'" (Gould, Stephen J. The Panda's Thumb, 1980, p. 181-182)