Slide showing two photographs of the 'Secondary sexual differences in confirmation, comb form, plummage form and color in domestic fowls.' Slide shows two black and white photographs of the 'Secondary sexual differences in confirmation, comb form, plummage form and color in domestic fowls.' Title below image reads: 'Fig, 68 - Secondary sexual differences in confirmation, comb form, plummage form and color in domestic fowls. Left, Silver Leghorn female; Right, Silver Leghorn male. (From Robinson)'. At the top of the slide "A: 92:" appears. Late 19th to early 20th century