. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. THE ORIGIN OF THE DEFINITIVE OVA Schron, 1863—cat and rabbit; Koster, 1868—man; Slawin- sky, 1873—man; Wagener, 1879—dog; Van Beneden, 1880— bat; Harz, 1883—mouse, guinea pig, cat; Lange, 1896—mouse; Coert, 1898—rabbit and cat; Amann, 1899—man; Palladino, 1894, 1898—man, bear, dog; Lane-Claypon, 1905, 1907— rabbit; Fellner, 1909—man) save that the work of Allen and those who follow takes advantage of recent discoveries of the nature of the oestrus cycle, and presents observations made upon ovaries taken at def- in
. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. THE ORIGIN OF THE DEFINITIVE OVA Schron, 1863—cat and rabbit; Koster, 1868—man; Slawin- sky, 1873—man; Wagener, 1879—dog; Van Beneden, 1880— bat; Harz, 1883—mouse, guinea pig, cat; Lange, 1896—mouse; Coert, 1898—rabbit and cat; Amann, 1899—man; Palladino, 1894, 1898—man, bear, dog; Lane-Claypon, 1905, 1907— rabbit; Fellner, 1909—man) save that the work of Allen and those who follow takes advantage of recent discoveries of the nature of the oestrus cycle, and presents observations made upon ovaries taken at def- inite times during the cycle. Since the embryogenesis of the primordial germ cells and the germinal epithelium are separate loo — and distinct it follows from the findings of these observers that the definitive ova of adult hfe do not arise from the primordial germ cells at all. Most of the earlier workers observed evi- dences of growth and thickening Fig. l. The frequency of mi- of the germinal epithelium or r^^rttiaTa'cf AUe"! even extensions of germinal epi- 1923. Open circles indicate com- thelium into the ovarian cortex. ^^,f ^^^^ on semi-spayed mice. Halt circles mdicate normal un- In some cases these signs of operated controls. Abscissae are activity were associated with stages of oestrus cycle; l, early pro the period of heat. Allen (1923) whose investiga- tions are perhaps pioneer to the most recent developments mitoses per mouse. (From the distinguished four stages in the ^^nerican Journal of Anatomy.) behavior of the germinal epithelium of the adult mouse during the oestrus cycle. The first, characterized by ex- tensive mitotic activity occurs just before and during oestrus (see Figure 1). The second is marked by a fairly abrupt decrease in mitosis frequency, and a position of the daughter epithelial cells one cell layer below the germinal epithehum. oestrus; 2, late prooestrus; 3, pro- oestrus to oestrus; 4, early oestrus; 5, oestrus; 6,
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