| Summary: | 1. In Hippa pacifica , mitotic division of germinal epithelial cells produces primary spermatocytes which, as sustentacular-like cells appear, divide meiotically to form spermatids. 2. Concurrently as spermatids metamorphose into spermatozoa, germinal epithelial cells renew their activity and again produce primary spermatocytes which, as they fill the sacculus, expel the spermatozoa. 3. A continuous spermatogenic mass enters the vas deferens, where an enveloping secretion from the epithelial cells bounding the lumen forms a thin sheath to the sperm mass. 4. The lumen (viewed in cross-section) becomes keyhole-shaped and a secretion from a wedge-shaped group of cells bounded by two deep crypts both surrounds the sheathed sperm mass and forms a ribbon-like supporting stalk and a broad, basal foot. 5. As the lumen again becomes circular (in cross-section), a secretion from the epithelial cells surrounds the completed spermatophore and forms the homogeneous matrix. 6. The spermatophore of H. pacifica is both macruran-like, because of its continuous, highly convoluted sperm mass, and anomuran-like, because of its raised spermatophore and broad foot. 7. Neither the anomuran-like spermatophore of a macruran, Parrabicus antarcticus , nor the macruran-like spermatophore of an anomuran, Hippa pacifica , justifies the inference that these two animals occupy a systematic position intermediate between the Macrura and the Anomura, but rather illustrates the need for consideration of many characters before postulating relationships.
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