46 S. ZUCKERMAN 



whether the cell is atretic or still normal" — and in such cases 

 she counted the cell as normal. Actually, anyone who has 

 tried to make successive counts of the atretic oocytes in an 

 ovary will know how numerous the marginal cases are, and 

 how difficult it is to obtain estimates which agree closely. 



A third criticism of Van-Eck's study is the unwarranted 

 assumption that the atresia which occurs as a result of X-ray 

 sterilization is identical in its nature, and in its duration, with 

 what occurs in the normal ovary. The only specific enquiry 

 into this point of which I know (Halberstaedter and Ickowicz, 

 1947), in fact, indicates that the first histological appearances 

 of atresia in the normal ovary are characteristically different 

 from those which herald atresia after X-irradiation. An ad- 

 ditional difficulty is that Van-Eck implicitly assumes that the 

 time taken for an oocyte to disappear after X-irradiation is 

 independent of the r dosage. The three monkeys which she 

 irradiated were given a total of 1200 r in two applications 

 through the dorsolumbar region of the body wall. It would be 

 extraordinary if the rate at which oocytes disappeared were 

 not increased if the same dosage were applied directly to the 

 ovaries, or alternatively, if a dose five times as great were 

 applied directly (see Lacassagne, 1913). 



The question whether oogenesis does or does not occur in 

 the mature animal has been so beset with equivocal fact and 

 arbitrary interpretation, that it is essential that new observa- 

 tions on the topic, which clearly has important practical im- 

 plications, should be marked by observational and conceptual 

 precision if they are not to multiply confusion. The first 

 point that needs to be settled is whether the experimental and 

 biometric data summarized on pp. 32-35 are consistent with any 

 thesis other than that oogenesis is in abeyance in the mature 

 rat or monkey. By "settling", I do not, of course, mean the 

 matching of fact with speculation — for example, disposing, 

 as do Aron et al. of the observation that oocytes can persist in 

 an ovary long after it has lost all recognizable signs of its 

 germinal epithelium, by suggesting that it is possible that some 

 unrecognizable or undefined derivative of that epithelium 



