Ernst Mayr quote-mined full passage
His quote mine? “What one actually found was nothing but discontinuities. intermediates between species are not observed”
Here’s a better context of that quote from Ernst Mayr’s What Evolution Is.
New types often appear quite suddenly, and their immediate ancestors are absent in the earlier geological strata. The discovery of unbroken series of species changing gradually into descending species is very rare. Indeed the fossil record is one of discontinuities, seemingly documenting jumps (saltations) from one type of organism to a different type. This raises a puzzling question: Why does the fossil record fail to reflect the gradual change one would expect from evolution?
All of his life Darwin insisted that this is simply due to the unimaginable incompleteness of the fossil record. Only an incredibly small fraction of organisms that had once lived are preserved as fossils. Often the fossil-bearing strata were on plates that were subsequently subducted and destroyed in the process of plate tectonics. Others were strongly folded, compressed, and metamorphosed, obliterating the fossils. Only a fraction of the fossil-bearing strata is presently exposed at the Earth’s surface. But it is even highly improbable that any organism ever becomes fossilized at all, since most dead animals and plants are either eaten by scavengers or decay. They become fossilized only when, immediately after death, they are buried by sediment or volcanic ash. Fortunately, occasionally a rare fossil is found that fills the gap between ancestors and modern descendants.