During self conjugation two cells from a 6-day old culture come together, bridges are formed between them and haploid products of meiotic division of their micronuclei are exchanged between the mating pairs. Two micronuclei are seen here which appear similar to the haploid pronucleus in the paper of Inaba et al. (Proc. Japan Acad. 42:394-398, 1966) which is passing through such a bridge in P. multimicronucleatum. In this micrograph two rounded micronuclei are lying very near the macronucleus. These may be the migratory and stationary pronuclei that will form the diploid synkaryon nucleus from which the new micronuclei and macronucleus will form after further mitotic divisions. Interestingly one of these nuclei appears to be in close contact with the macronucleus. TEM taken on 3/4/80 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 5,000X. Bar = 1µm.