polyembryony

n.
Development of more than one embryo from a single egg or ovule.

polyembryonic pol'y·em'bry·on'ic (-brē-ŏn'ĭk) adj.

(pŏl'ē-ĕm'brē-ə-nē, -ĕm-brī'-)
n.

Development of more than one embryo from a single egg or ovule.

The production of two or more embryos from one ovum, e.g. monozygotic twins. Armadillos are the only consistently polyembryonic mammals.
It is a phenomenon in some helminths, e.g. Gyrodactylus spp., in which viviparous adults produce trematodes that are identical with themselves and as larvae they carry larvae within their uteri which contain larvae in their uteri. The rate of reproduction can be very high. Also occurs in some insects in which fertilized eggs give rise to a number of larvae.