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The theory of Darwin that every separate part of the organism reproduces itself in the progeny, each ovule and spermatozoon containing a particle or germ thrown off from each separate unit in the parent organism.

The doctrine that in reproduction each cell of the parent body is represented by a particle.

Of Darwin, the hypothesis for the provisional explanation of such facts as the inheritance by offspring of both original and newly acquired characters of parents, the appearance of characters belonging to remote ancestors (atavism), and the appearance in metembryonic or even adult life of characters before latent. The hypothesis depends on the assumption that every living cell of the organism at all periods of development throws off gemmules or molecules capable of reproduction. These circulate through the system and become aggregated in the reproductive cells, and can give rise to a new individual, as by the buds of plants or by the combined action of distinct sexual elements. In each case the gemmules give rise to cells corresponding to those from which they originated in the parent body. Generally the gemmules develop in the following generation; but they may be permanently lost or may remain quiescent and develop after several generations. [Gr.]