摘要: acteristic form (with nipples). Mivart (perhaps)' and Darwin (1859) suggested that cutaneous glands evolved to a mammary function. Rein (1882) hypothesized mammae developed directly from ectoderm. Gegenbaur (1886) discussed the resemblance probably homology of monotreme lactiferous tubular sweat glands. He believed, however, other mammals derived their sebaceous .glands. Benda (1894) Brouha (1905) now widely accepted theory milk in all are Myers (1917) similarity anlagen hairs. No fossil evidence on origin is available.