Pronucleus

(pro-nu' -kle-us). In biology, the name given by Ed. van Beneden to one of the two nuclear elements of a newly fecundated ovum, the male and the female pronucleus, the fusion (conjugation) of which results in the formation of the first embryonic nucleus. The nucleus which appears within the ovum after the formation of the polar bodies is the female pronucleus. According to Hertwig, the head of the spermatozoid is transformed directly into the male pronucleus, while Salensky holds that it is first di olved and provokes secondarily the formation of the male pronucleus. P., Segmentation, the nucleus of the germ. P., Sperm. Synonym of P., Male.