Sperm banks impose their own limits on the number of pregnancies obtained from exported sperm. Gametes (sperm and ova) are haploid cells. Testosterone is necessary for normal sperm development. The penis provides a passageway for sperm and urine. The first category produces and stores sperm (spermatozoa). The secretions from the female genital tract aid in sperm migration. The testes release a hormone that controls the development of sperm. Fusion of the plasma membranes of the sperm and egg are likely mediated by bindin. Here, the egg is able to become fertilised with sperm. Secondly there is an adhesive compatibility between the sperm and the egg. ZP3 is sufficient though unnecessary for sperm/egg binding. All the haploid sperm and eggs produced by meiosis received one chromosome 7. Spermaceti occurs in large amounts in the head oil of the sperm whale. Most sperm cells have centrioles in the sperm neck. The union of sperm and eggs is random.