When does were inseminated with spermatozoa from the lower part of the corpus epididymidis of individual bucks, fertilization rates varied greatly and in almost every case, cleavage occurred later than has been reported following the insemination of ejaculated spermatozoa. The retardation occurred both when spermatozoa were deposited in the uterus and in the Fallopian tube, with the exception of those animals showing the greatest delay, where tubal insemination resulted in fewer eggs being fertilized and in cleavage being more retarded.
It appears that the phenomenon of delayed fertilization resulting from the use of epididymal spermatozoa is not due to an abnormal rate of sperm migration, but to the need for an extended period of capacitation. The epididymal spermatozoa of some bucks required more than twice as much time for capacitation as that reported to be necessary for ejaculated spermatozoa. It is suggested that the process of sperm capacitation is primarily a continuation of the maturation process begun in the epididymis of the male.