318 Umversitu of California Publications in Zoology [Vol. 20 



In the one- and two-cell stages, when many chromatoidal bodies, 

 as well as the nuclei, fill the narrow space between the glycogen mass 

 and the periphery, the nuclei are exceedingly difficult to differentiate, 

 particularly if the chromatin granules have left their position on the 

 nuclear membrane. In a few cases only have the cysts been devoid, 

 or nearly so, of chromatoidal material (pi. 29, figs. 6, 7). The nuclei 

 are often obscured also by the change in the staining reactions of the 

 chromatin that may be noticed at this stage, in its failure to take 

 a dark stain with iron-haematoxylin or in its ease in destaining. 

 Frequently, as the chromatin gathers at the center of the nucleus, it 

 stains less intensely with iron haematoxjdin, appearing as a grey mass 

 with a few darker staining granules within it (pi. 29, fig. 3). Later 

 the central mass takes an intensely dark stain and at the same time 

 shows a considerable increase in volume (pi. 29, fig. 4). 



It is impossible to say whether any chromatin substance is extruded 

 from the nucleus, owing to the amount of darkly staining material 

 found in the extranuelear regions. There is no evidence of an 

 exchange of material in either direction, though it may well take 

 place. It is equally impossible, however, to consider the abundant 

 chromatoidal bodies as formed by nuclear extrusions alone, as they 

 are often present in great quantity and size before division begins 

 (pi. 29, fig. 1). Their abundance in the earlier stages of mitosis and 

 their gradually lessening quantity as mitosis proceeds, as is the case 

 also with the glycogen, would seem to indicate that both these sub- 

 stances serve as reserve food materials that are gradually iised up 

 in the great metabolic activity required by the repeated processes of 

 mitotic division. The glycogen is formed before the chromatoidal 

 bodies appear, and it likewise is absorbed before the latter are. Cysts 

 containing more than four nuclei very rarely show any traces of 

 glycogen, while the presence of chromatoidal bodies is frequently 

 noted in such cysts. 



About the time the chromatin granules have all disappeared from 

 the nuclear membrane, the chromatin in the central mass has assumed 

 the appearance of small, oblong granules, or rods, without definite 

 number or arrangement, but scattered through the major portion of 

 the interior of the nucleus (pi. 29, figs. 4, 5). A definite spireme or 

 skein was not observed, nor could the formation of the chromosomes be 

 followed in detail. The mass of granules becomes less in amount, 

 either by condensation or other metabolic change, and the double 

 chromosomes appear (pi. 29, fig. 7, lower nucleus). 



