38 S. ZUCKERMAN 



by a cluster of satellite cells." The further inference about 

 oogenesis, implied by Aron et aL's reference to the paper, is not 

 even mentioned. The only paper cited in connection with this 

 particular issue, and which, in fact, bears critically on the 

 question of oogenesis, is that of Hamlett (1935) on the arma- 

 dillo. It does so, not because it emphasizes the topographical 

 relations of oocytes to the germinal epithelium, but because it 

 describes nuclear changes that may be indicative of oogenesis 

 (see later). 



Observations about the position of cells in the ovary are far 

 too equivocal to sustain conclusions about the occurrence of 

 oogenesis in adult life. Oogenesis is a process. As I have 

 emphasized before (Zuckerman, 1951), to infer that it occurs 

 from a study of histological sections implies that separate and 

 distinct phases of the process, each necessarily viewed in 

 isolation can, as it were, be set in continuous motion by a 

 dynamic interpretation. This might be a reasonable exercise 

 if there were clear-cut and generally accepted cellular stages 

 which in the mature ovary linked an indisputable oocyte with 

 some other and equally well-defined cellular constituent of the 

 ovary, for instance, a cell of the germinal epithelium. But 

 this is not so. Some writers, for example Allen (1923) and 

 Bullough (1942), have merely assumed that if a cell of the 

 germinal epithelium divides, one or both of the daughter cells 

 will differentiate into an oocyte, and only a very few have 

 attempted to define the cellular stages which, in the adult 

 ovary, might link an oocyte with a cell of the germinal 

 epithelium, or with any other cellular component of the ovary. 

 The majority of histologists have completely failed to con- 

 vince themselves on this point. 



I have elsewhere suggested an alternative, and far simpler, 

 explanation of the proliferative powers of the germinal epithe- 

 lium (Zuckerman, 1951). It is that the capacity of the cells 

 of the adult germinal epithelium to subdivide reflects the 

 extensive cyclical changes which occur in the shape and 

 size of the ovary as follicles mature and burst, and tear the 

 surface of the ovary, and as corpora lutea develop. These 



