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n. The formation, development, and maturation of an ovum.

n. The formation and development of an ovum.

n. The development, or mode of origin, of the ova.

n. The genesis or origin and development of the ovum.

n. development of ova

"This marine worm, first described in 1949 as an acoel flatworm and later claimed as either an early metazoan offshoot or a primitive deuterostome, has recently been affiliated with primitive bivalve molluscs, based upon a study of gamete development oogenesis and an analysis of sequence data from both 18S rRNA and mitochondrial genes."

spermatogenesis   

gametogenesis   

oogenetic