88 GARDINER. [Vol. XV. 



owing apparently to the stain-absorbing substance of the 

 chromatin having been leached out into the cytoplasm. It 

 frequently happens that sections through ova containing such 

 fragments of the nucleus are perfectly unfit for study, owing to 

 the deepness of the stain, while other ova in the same worm and 

 on the same slide, and which, therefore, have been subjected 

 to exactly the same treatment, are not at all overstained. 



The larger portion of the nucleus as shown in Fig. 14 

 remains in about the center of the ovum and undergoes a rapid 

 disintegration. The granular structure, in which the chroma- 

 tin particles are so distinctly separated from the linin (Fig. 13), 

 has completely disappeared, giving place to an ill-defined, 

 muddy-looking mass, as if the stainable substance of the 

 chromatin had leaked out and contaminated the hitherto clear 

 linin as well as the cytoplasm. This must indicate a chemical 

 change in both chromatin and linin. Also it should be noted 

 that this muddy appearance extends out around the amphiaster, 

 as if this structure while moving away from the degenerating 

 nucleus had dragged with it some color-absorbing substance. 

 The only chromatin which at this stage retains its former 

 power of being sharply differentiated by stain are the clumps 

 within the amphiaster, from which material the chromosomes 

 are to be formed. While the amphiaster moves on its way 

 to the surface of the ovum, the shattered portion of the 

 nucleus gradually fades in distinctness, the cytoplasm around 

 it still staining very deeply. Gradually, however, the nuclear 

 substance is so completely assimilated by the cytoplasm that 

 no trace of it remains, and the cytoplasm stains no more deeply 

 than before the nuclear wall was ruptured. The relative quan- 

 tity of substance taken from the nucleus to form the amphi- 

 aster as compared with the quantity assimilated or digested 

 by the cytoplasm will be discussed later (p. 99). 



While this amphiaster still adheres to the remnant of the 

 nucleus, its length from aster to aster is of course greater than 

 the diameter of the nucleus. When, however, it once breaks 

 away from it, it is noticeable that instead of the asters drawing 

 apart, they begin to draw toward one another. Thus the length 

 shown in Fig. 14 is somewhat less than the diameter of the 



