36 S. ZUCKERMAN 



oogenesis which have so far emerged from studies in my own 

 laboratory. It is necessary to consider them in the light of the 

 contrary statements that have been made more recently by 

 Aron, Marescaux and Petrovic (1952, 1954a, b); by Van-Eck 

 (1955); by Burkl (1954, 1955); and by Burkl and Kellner 

 (1954a, b, 1955). 



The new observations reported by Aron, Marescaux and 

 Petrovic (1954&) relate to the apparent occurrence of differen- 

 tiating oocytes in the ovary of the mature guinea pig. They 

 present their findings in the context of a general review, in 

 which they refer to various statements made by other workers 

 in support of the alternative views (a) that oogenesis occurs 

 only during embryonic life; (b) that it continues for a variable 

 period after birth; (c) that all the oocytes formed during 

 embryonic life are destroyed shortly after birth, and are then 

 replaced by a new generation of oocytes; and (d) that new 

 oocytes are formed throughout reproductive life. Aron and his 

 collaborators come down firmly in favour of the last of these 

 hypotheses, and cite a number of papers which they believe 

 prove that oocytes can be formed either from the germinal 

 epithelium or from cord-like invaginations of this epithelium 

 within the substance of the mature ovary. Their selection of 

 the literature is, however, arbitrary; and they make little 

 attempt to analyse critically the papers they cite. Indeed, at 

 least a few are quoted in a sense different from what their 

 authors apparently intended. For example, Nunes (1932) is 

 referred to as one who has helped establish " with certainty" 

 that oocytes differentiate from invaginations of the germinal 

 epithelium within the substance of the ovary. In fact, all his 

 paper records is that in the adult rabbit ovary follicles are often 

 closely related to epithelial invaginations, and his own con- 

 clusion — "on ne peut done nier d'une maniere absolue la 

 neoformation ovigene dans l'ovaire adulte" — is much less 

 categorical than is implied by Aron et aZ.'s references. Lane- 

 Claypon (1905) and Pincus and Enzmann (1937), who are 

 among many others who have studied the rabbit ovary, and 

 both of whom are also cited by Aron et ah, reached quite 



