294 H. M. KINGERY 



and resorbtion of these latter and their foUicles, as well as by the 

 growth of the whole ovary. 



From this it is apparent that the potentiality of the germinal 

 epithelium for germ-cell formation lasts for a relatively long time 

 in the mouse. At birth, the cells of the germinal epithelium 

 seem equally capable of developing into oocytes, follicle cells, 

 or epithelial cells, and it is not evident just what the factors are 

 which determine their eventual fate. As the ovary becomes more 

 mature and the cells more differentiated, this potentiality of the 

 cells of the germinal epithelium is lost and after sexual maturity 

 no more egg-cells or folhcle cells are derived from the epithehum. 



The question of synizesis and synapsis'^ has been given marked 

 attention during the last few years. Whether synizesis repre- 

 sents a real condition in the development of the germ cells (egg 

 or spermatozoon) has been discussed quite thoroughly and will 

 be taken up only briefly here. Reference is made to the works 

 of von Winiwarter and Sainmont ('08), Duesberg ('08), Meves 

 ('07), and others who discuss the question and the literature. 

 Here it will be enough to say that Meves, Duesberg, McClung, 

 and many others consider synizesis an artifact due to faulty 

 fixation. The first two authors, however, admit that there is at 

 a definite period in the development of the germ cells, a tendency, 

 more or less marked in different forms, on the part of the chro- 

 matin to contract when brought into contact with the fixative. 

 On the other hand, von Winiwarter and Sainmont, and probably 

 a majority of those who have given the matter consideration, 

 believe that synizesis is a normal stage in the development of the 

 germ cells, of rather marked theoretical importance. 



The existence of synapsis or a conjugation of chromatin threads 

 is affirmed and denied; and those who believe it takes place are 

 not agreed on the manner of its occurrence. Union side by side 



^ There is some confusion in regard to the usage of these terms. Von Winiwar- 

 ter and Sainmont use 'synapsis' to mean a contraction of the chromatin to one 

 side of the nucleus. The better usage seems to be, however, to restrict this term 

 to the conjugation of the chromatin threads or chromosomes, and to employ 

 'synizesis' to apply to the stage where the chromatin is contracted in the nucleus, 

 as McCluiig suggested in 1905. Accordingly, the terms will be used here in this 

 sense. 



