de Vries first published his discovery, in 1902

that in the offspring even of thoroughly pure-bred stocks, avery small number of individuals, say two or three in tens ofthousands, turn up with small but 'jump-like' changes, theexpression 'jump-like' not meaning that the change is so veryconsiderable, but that there is a discontinuity inasmuch asthere are no intermediate forms between the unchanged andthe few changed. De Vries called that a mutation.