Ookinesis in Cerebratuhis l.actons. 357 



is now fonnd precipitated in the form of floccnlent masses, as though 

 another kind of proteid had entered the nuclear area, and had 

 mixed with the nuclear fluid. The precipitated granules are of 

 fairly largo size. They take a strong haimatoxylin stain, and in this 

 respect they resemble chromatin (basichromatin). Yet that they do 

 not contain any basichromatin at all, is demonstrated by Auerbach's 

 method, with which they take a strong fuchsin stain. There are 

 several instances in which a chromatin diminution is said to take 

 place at the formation of the first maturation figure (Wilson and 

 Mathews, '95; Gardiner, '98; Griffin, '99; Coe, '99; Conklin, '02). 

 But in these cases the writers may have taken the precipitated 

 nuclear fluid for chromatin, simply because it is stained with hsema- 

 toxylin. This phenomenon, I think, can hardly be called chromatin 

 diminution. 



The mass of precipitated nuclear fluid (residual substance of 

 germinal vesicle, Lillie, '06) moves towards the animal pole taking 

 a columnar shape around the first maturation figure (PI. IV, Fig. 

 59). In the eggs kept unfertilized for several hours this plasm 

 spreads out at the animal region, forming a layer thick at the middle 

 and thinning towards the periphery (Kostanecki and Wierzejski, 

 '96, p. 370; Kostanecki, '02, p. 272; Wilson, '03, p. 446, foot-note, 

 Yatsu, '04, p. 134). In the cleavage stages the precipitated nuclear 

 fluid, which is found outside the spindle at the metaphase, is ab- 

 sorbed to the equatorial plane at the anaphases (Text Fig. C, 1 and 

 2). The portion of the fibres included within this plasm is thicker 

 and stains darker than the rest. This nuclear plasm seems to play 

 an important role in the formation of the diastem {vide infra) 

 and the midbody. I can, however, find no evidence that it is directly 

 converted into the cell membrane as Ehumbler maintains ('97, pp. 

 696-697; '9S, pp. 549-552; '99, p. 200). 



It is noteworthy that at the pro])hase of the cleavage mitoses the 

 rays Avhich grow towards the nucleus from the astral centres (the 

 rays which give rise to both the spindle and the chromosomal fibres) 

 are after the dissolution of the nuclear walls, composed of two por- 

 tions ; namely, an extranuclear and an intranuclear part. The latter 

 are thicker and stain more deeply (PI. I, Fig. 4). The similar dif- 



