In a large number, probably the majority, of Bryophyta the antheridium on dehiscence under water discharges the spermatocytes in a mass. This mass is pushed out by a liquid which accumulates in the base of the antheridium. On reaching an air-water surface the spermatocytes spread apart rapidly and form a layer on the surface in which they are regularly spaced apart. This surface spread is evidently correlated with the presence of fat in the spermatocyte mass. This fat lowers the surface tension and causes the spreading. In Sphagnum and some liverworts where surface spreading does not occur fat has not been detected in the spermatocyte mass. This spreading action is evidently of considerable biological significance and plays an important part in carrying a supply of spermatocytes rapidly to the neighbourhood of the female organ where the free sperms are liberated and are then directed chemotactically to the female gamete. The distribution in a surface layer instead of throughout the liquid offers an explanation of why insects play an effective part in carrying spermatocytes from male plants to female plants in dioecious mosses.