Mature ova or spermatozoa will not normally divide if left to themselves, but that is because they are specialised to secure amphimixis, not because their powers are in any way declining or impoverished.
"Herbert Spencer"
J. Arthur Thomson
He attributed variation partly to the union of gametes containing various determinants, which he termed amphimixis: this, however, would introduce nothing new.
"Hormones and Heredity"
J. T. Cunningham