318 Elliot R. Downing, 



separates the nuclear region from the overlying layer of ectodermal 

 plates or from adjacent eggs (Fig. 18, Plate 12). 



28. The network of the nucleus is constantly becoming plainer; 

 the chromatin granules become distinct upon the network (Fig, 12, 

 Plate 12). 



29. The nucleus continues to decrease in size: when the first 

 polar body is about to be formed the nucleus (Fig. 13, Plate 12), is 

 only about one three-hundredth the volume that it had at the 

 beginning of the maturation phenomena (Fig. 8, Plate 11). During 

 maturation there is an antithesis of constancy in the nucleo-plasma 

 relation, a continuous change in the relation. 



30. The decrease in volume of the nucleus is accompanied by 

 the ejection of much chromatin from the nucleus. Brauer claims 

 to have evidence that it passes out directly in granules through 

 the nuclear wall into the plasma: I am unable to confirm this and 

 only know that it gets out and appears as deeply staining granules 

 about the nucleus. The remaining nuclear chromatin hardly stains 

 as deeply, in many stages as this escaped chromatin ; it is, con- 

 sequently, easy to overlook the nucleus lying obscured by these 

 surrounding granules. With iron-haematoxylin the yolk stains very 

 deeply so that the egg sections, mounted to show the chromatin 

 changes, will be very black because of the yolk except at the one 

 spot where the nucleus lies (Fig. 1, Plate 11, upper left hand egg). 



31. I must take exception to the method of appearance of the 

 chromosomes as described by Brauer and confirmed by Tannreuther; 

 they do not form directly from the granules about the nucleus but 

 these granules disappear as noted above and the chromosomes are 

 formed in quite the regular way. All stages may not be presented 

 because of lack of sufficient material, but this much is certain: The 

 nuclear network of linin threads with the chromatin particles upon 

 it becomes coarser (Fig. 12, Plate 12), and finally a spireme stage 

 is formed quite homologous to that found in the spermatogonia. I 

 can not determine exactly how this segments to form the chromo- 

 somes. 



32. Twelve chromosomes are formed; Brauer decided the number 

 was 12 — 14. They are rod shaped, much more elongate in my 

 specimens than Brauer figures and are seen, in favorable cases to 

 consist of four chromomeres each (Fig. 15, Plate 12): they measure 

 about 2-5 ," long- and 0-4 u in diameter. 



