Conjugation was studied in Schizosaccharomyces pombe using liquid media. Nitrogen, which was growth-limiting in a synthetic medium, had to be consumed completely before conjugation could start. Conjugation was preceded by sexual agglutination. Agglutinability was not constitutive in heterothallic strains. It only developed when cells of h (+) and h (-) mating type were grown in mixed culture for at least 2.5 hr before the start of conjugation. 