300 H. M. KINGERY 



tion. It might not be going too far to conclude that in cases 

 where synizesis and synapsis occur as undoubted facts, the 

 cells are in a more or less marked condition of degeneration. In 

 some cases, such as the primitive germ cells of the mouse, the 

 cells of the second proliferation of the cat (von Winiwarter and 

 Sainmont), etc., the degeneration is so pronounced that the 

 cells never recover. In other cases, for example synizesis and 

 synapsis, as described in the germ cells of an increasingly large 

 number of forms, the degenerate condition is so slight that al- 

 though it brings about synizesis and, in many instances, synapsis, 

 the cells recover and proceed to maturation. 



It was stated in the earlier part of this paper that the egg- 

 cells of the first or embryonic proliferation in the mouse all 

 degenerate and disappear. The evidence for this is both direct 

 and circumstantial. In ovaries of mice, from about seventeen 

 days post partum up to those sexually mature and adult, egg- 

 cells in their follicles may be seen in various stages of degeneration 

 and atresia. Usually the atretic follicles are large, and at first 

 are located near the center (future medulla) of the ovary, but 

 smaller degenerating follicles are in the primitive cortex as well. 

 As stated above, some of these degenerating egg-cells undergo a 

 degenerative fragmentation and may form a first polar body 

 and second polar spindle, and may even break up into fragments, 

 with or without nuclei, so that the whole process resembles 

 parthenogenesis (Kingery, '14). This is evidence, of course, 

 that a large number of these germ cells of embryonic origin 

 degenerate and are resorbed. Furthermore, in ovaries from a 

 few days after birth to sexual maturitj^ there is 9 peripheral 

 zone of egg-cells in primary follicles made up of a single layer of 

 flattened cells. This zone, which may be from three to six or eight 

 cells deep, is composed of definitive oocytes I, formed from the 

 germinal epithelium after birth and located in and under the 

 tunica albuginea. A study of ovaries between birth and sexual 

 maturity shows that, in the mouse as in other forms, there is 

 formed an over-supply of oocytes, and a vast number of these 

 egg-cells must fail to reach maturity. The development and 

 differentiation of the ovary has had a centrifugal direction all 



