Illustrations showing various stages of the formation of a chicken embryo, printed as Table IV in Marcello Malpighi's Dissertatio epistolica de formatione pulli in ovo (London, 1673). The images show: a chicken embryo after the eighth day of incubation (Fig. XXI); embryo with albumen and yolk sac at the tenth day of incubation (Figs. XXII); embryo with beginnings of feathers at the twelfth day of incubation (Fig. XXIII); a nearly fully developed chicken and its heart (Figs. XXIV) at the fourteenth day of incubation; part of the intestinal system of a four-day-old chicken (Fig. XXV).