The stages of spermatogenesis and the structure of the primary oocyte of Sphaerostoma bramae were studied in material fixed in Bouin and Flemming's fluid and in preparations treated according to the Kolatchev and the Feulgen techniques.

Chromosome counts of primary and secondary spermatocytes indicate that the diploid number is twenty-four.

The stages of spermatogenesis, in general, conform to the usual pattern of this process in digenetic trematodes. The spermatogonia, spermatocytes and early spermatids are not connected together by central strands, nor by a central disk, as is claimed for some other species. A study of sections stained in haematoxylin and of Feulgen preparations showed that the spermatozoon is composed of an elongate nucleus and a tail. It was not possible, with the methods employed during the present investigation, to determine the fine structure of the tail.

The primary ovarian oocytes are in the interphase or in early prophase of the first maturation division. There is evidence that material is extruded from the nucleus to the cytoplasm.

The Golgi elements of the male germ-cells are revealed in Kolatchev preparations as short rods and filaments. The Golgi elements of the spermatid are eliminated in the residual cytoplasm. Mitochondria, in the form of granular bodies and short rods, were visible in spermatogonia, spermatocytes and spermatids. Those of the spermatid remain in the residual cytoplasm.

Short, rod-like Golgi bodies are present in the primary oocytes. In the young cells they form a compact mass situated close to or in contact with the nuclear membrane. Later, the elements spread out through the cell. Granular and rod-shaped mitochondria are concentrated in a single mass at one pole of the nucleus or in two masses at opposite sides of the nucleus. A few mitochondria are scattered through the cytoplasm.