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Germ plasm or polar plasm is a zone found in the cytoplasm of the egg cells of some model organisms (such as Caenorhabditis elegans, Drosophila melanogaster, Xenopus laevis), which contains determinants that will give rise to the germ cell lineage. As the zygote undergoes mitotic divisions the germ plasm is ultimately restricted to a few cells of the embryo, these germ cells then migrate to the gonads.

The germ plasm theory is a hypothesis concerning the ability to become germ cells, which is now proven wrong. ^[1]

The term germ plasm was first used by the German biologist August Weismann (b.1834-d.1914) to describe a component of germ cells that he proposed were responsible for heredity, roughly equatable to our modern understanding of DNA. August Weismann formulated the now defunct germ plasm theory in 1893, in which he stated that the germ plasm was the essential nuclear part of germ cells, that it remained qualitatively unchanged from the zygote (in contrast with somatic cells) and was responsible for heredity. In other words it states that a gene's determination was sealed as it, and each of its offspring received fewer and fewer genes from what he called the "germ plasm." (That there is only a set "amount" of "germ plasm" (what we know as genes) and that it was gradually divided amongst the offspring). Cases such as Dolly (the famous cloned ewe) which, via somatic cell nuclear transfer, proved that adult cells retain a complete--as opposed to Weissman's increasingly determined gradual loss of genetic information--set of information; finally putting Weismann's theory to rest.

• Germplasm, the collection of genetic resources

1. ^ The Germ-Plasm: A Theory of Heredity by August Weismann