The fusion of the ovum and spermatozoon is called conception, fertilization, or impregnation, and initiates the beginning of a new life. The ovary only produces one ovum per month, but as many as 200,000,000 spermatozoa each 0.05 mm. are deposited in the vagina when coitus takes place. At this time the cervix secretes a flow of alkaline mucous that attracts the spermatozoa and in which they are propelled by the rotary movement of their tails. A limited number of spermatozoa reach the Fallopian tube; a few may penetrate, but only one fuses with the nucleus of the ovum.