Investigations into the Fertility of Epididymal Spermatozoa

Rabbit spermatozoa from the distal corpus epididymidis fertilized 52 % of 110 ova when inseminated at the same time as HCG injection,or 93’-l3 hr before ovulation in the re-cipients. Ejaculated spermatozoa fertilized 84 % of 90 ova under the same experimental conditions. Ova fertilized by epididymal spermatozoa showed delayed cleavage; 30 % had still not divided 25 hr after HCG, as compared with 17 % of the controls. When ovulation was delayed by 6 hr, there was a significant advance in the stage of cleavage among ova ferti-lized recovered in both the experimental and control groups (15 and 6%, respectively, had not divided), however fertilization rates were unchanged. Thus, prolonging the incubation of spermatozoa from the distal corpus in the female did not enhance their fertilizing ability. When spermatozoa from the proximal corpus epididymidis were inseminated into the uter-ine horns at the same time as HCG injection, 2 of 15 females had ova fertilized: when they were inseminated 6, 12, and 18 hr before HCG, only 1 of 28 females had fertilizedova. No fertilization was observed when insemination was made directly into the oviducts. Fertilization with spermatozoa from the proximal corpus epididymis appeared to result from variations between males in the number of fertilespermatozoa to be found in this