COMPETITION BETWEEN FRESH AND AGED SPERMATOZOA IN FERTILIZING RABBIT EGGS

Abstract

Chance is ordinarily considered to be responsible for determining which spermatozoon fertilizes an egg. Results from experiments on competitive fertilization in hens tend to disprove this concept. When fresh and aged cock spermatozoa competed directly, the eggs were fertilized by the fresh spermatozoa, although the aged spermatozoa alone were capable of fertilization (Warren & Kilpatrick, 1929). The cocks were mated alternately at intervals of several days, and the last cock always sired the offspring. When spermatozoa from two apparently equally fertile males of different strains of mice or breeds of rabbits were mixed in equal numbers, one male consistently sired a higher proportion of the offspring (Edwards, 1955; Beatty, 1960) adding further doubt to the concept that chance alone determines which spermatozoon fertilizes an egg. Spermatozoa, whether motile or immotile, and inert particles