44 S. ZUCKERMAN 



purports to show that the rate of neoformation of oocytes in 

 albino rats increases after hypophysectomy. Oocyte counts 

 are given for this study, but their statistical analysis, again, 

 does not bear out the conclusion stated. In the first experi- 

 ment the mean number of oocytes for eight prepubertal 

 hypophysectomized animals was 3840 ± 300, and for five 

 controls 3180 ± 170. This difference is not significant statisti- 

 cally. In a second experiment, carried out on mature animals, 

 the corresponding figures for eight hypophysectomized animals 

 are 2650 ± 230 and for five normal controls 2580 ± 230. Again, 

 the difference does not approach statistical significance. 

 Analysis of these figures, in fact, shows that the results of 

 Burkl's experiments agree closely with those of Ingram (1953), 

 carried out in my own laboratory. They fail to demonstrate a 

 significant increase in the number of oocytes after hypo- 

 physectomy, but do indicate that the usual rate of decline in 

 the numbers of oocytes may slow down after the pituitary is 

 removed. 



Van-Eck (1955) attempts to reach a conclusion about the 

 occurrence of oogenesis in the adult ovary of the rhesus 

 monkey from an experimental estimate of the time it takes 

 an oocyte to become atretic and to disappear. This work 

 is based on oocyte counts of fourteen immature (represent- 

 ing ten animals) and seven mature ovaries (representing four 

 animals). The time taken for a follicle to become atretic 

 was estimated from experiments on three young adult 

 monkeys which were irradiated with 1200 r (600 r on two 

 successive days) between the 19th and 22nd day of the men- 

 strual cycle, and ovariectomized 7, 10 and 14 days later 

 respectively. Oocytes surrounded by more than one layer of 

 cuboidal cells were not present after 7 days, and after 14 days 

 the only oocytes present were those surrounded by one layer 

 of epithelial cells. Van-Eck concludes that "once atresia 

 occurs in a follicle the process is invariably completed within 

 two weeks ; for the small growing follicles the process takes less 

 than one week." 



On the assumption that the time taken for atresia to occur 



