 Between 1877 and 1878 , Oscar <unk> published several studies on the fertilization of sea <unk> eggs , showing that the nucleus of the sperm enters the <unk> and fuses with its nucleus . This was the first time it was suggested that an individual develops from a ( single ) nucleated cell . This was in contradiction to Ernst <unk> 's theory that the complete phylogeny of a species would be repeated during embryonic development , including generation of the first nucleated cell from a " <unk> " , a <unk> mass of primordial <unk> ( " <unk> " ) . Therefore , the necessity of the sperm nucleus for fertilization was discussed for quite some time . However , <unk> confirmed his observation in other animal groups , including amphibians and molluscs . Eduard <unk> produced the same results for plants in 1884 . This paved the way to assign the nucleus an important role in heredity . In 1873 , August <unk> postulated the equivalence of the maternal and paternal <unk> cells for heredity . The function of the nucleus as carrier of genetic information became clear only later , after mitosis was discovered and the <unk> rules were rediscovered at the beginning of the 20th century ; the chromosome theory of heredity was therefore developed . 
