||P. Primakoff, D.G. Myles, Cell–cell membrane fusion during mammalian fertilization, FEBS Lett., 581 (2007), pp. 2174–2180 DOI: 10.1016/j.febslet.2007.02.021 AND M. Zuccotti, A. Piccinelli, N. Marziliano, S. Mascheretti, C.A. Redi, Development and loss of the ability of mouse oolemma to fuse with spermatozoa, Zygote, 2(1994), pp. 333–339PubMed ID17328899, 8665163
||P.155 bottom paragraph: "Before a sperm and egg (or oocyte) can fuse to initiate development, they must prepare for fusion-competence so that their plasma membranes can merge (primary source Primakoff and Myles, 2007). Mouse oocytes, for example, are not at all fusion-competent until they reach a diameter of approximately 20 μm and do not normally fuse with sperm until they are 80 μm in diameter (primary sources). Mammalian sperm are not fusion-competent until they have undergone both capacitation in the female reproductive tract and the acrosome reaction, during which the outer membrane of a special organelle fuses with the sperm plasma membrane."