Chemotoxis or chemical attraction of male gametes is found in bryophytes and pteriodophytes. The archegonium releases chemical substances which attract male gamates. In animals the male gametes are generally attracted by a trapping effect, although  chemotaxis may also operate in coelentrates and fishes.

Fertilizin-antifertilizin Reaction. The Jelly covering of the egg had hypothetical receptor molecules which he termed fertilizin. The fertilizing molecules have receptor sites which are complementary to the surface molecules (antifertilizin) on the sperm head. The fertilizing molecules bin the sperms at receptor sites and cause clumping.



The modern view holds that the fertilizin and antifertilizin are analogous to a lock and key respectively. During agglutination the antifertilizin keys fit into the fertilizing locks. Fertilizin has high specificity and will only agglutinate sperms of a particular species. This is thought to be due to a definite molecular arrangement of the amino acid and monosaccharides in the fertilizing molecule of a species.

The main source of fertilization is believed to be the jelly coat or the vitelline membrane. This fertilization is called jelly coat fertilizin. The jelly coat probably originates from the follicles of the ovary. Fertilizin has also been found in the plasma membrane of some eggs. This fertilizin, called cytofertilizin, is probably the real receptor substance for sperms. It probably originates mainly in the egg cell. Feritilizin has been demonstrated in mollusks, echinoderms, annelids and chordates, and is probably found in the gamates of all phyla. Feritilizin has been demonstrated in mollusks, echinoderms, annelids and chordates, and is probably found in the gamates of all phyla. Removal of fertilizin by enzyme digestion, and of antifertilizin by acid treatment generally tends towards reduction in fertilization.