1912] YAMANOUCHI—CUTLERIA 451 



The nucleus of the male gametangium initial is considerably 

 larger than is common in cases of vegetative mitosis (fig. 18). The 

 chromatin network of the resting nucleus is marked by a number of 

 knots mixed with broken fibrils (fig. 18). The chromatin knots 

 increase gradually in size in prophase and finally break up into 24 

 chromosomes (fig. 19). Up to this stage the nucleolus remains 

 without apparent change. When the chromosomes begin to be 

 arranged at the equatorial plate, the nuclear membrane becomes 

 contracted, and at the completion of the nuclear figure the decrease 

 of the diameter of the nucleus is remarkable (fig. 20). Two dis- 

 tinct centrosome-like structures now are present at metaphase. 

 While the nuclear membrane still persists, the chromosomes split 

 longitudinally and half of each chromosome proceeds to each pole 

 (fig. 22). The nucleus passes into telophase, two new daughter 

 nuclei are formed, and then the subsequent divisions occur. In the 

 second division the two nuclei may undergo mitotic changes simul- 

 taneously, both showing 24 chromosomes in prophase (fig. 23), or 

 one may proceed more rapidly than the other. Figs. 24 and 25 

 show the latter case; the nucleus of the upper cell is in prophase, 

 showing 24 chromosomes, and that of the lower cell is in metaphase. 

 In figs. 24 and 25, in spite of the apparent similarity in the size of 

 the lower cells, the difference in the size of their nuclei at metaphase 

 is remarkable. Sometimes the nucleus of the upper cell is far 

 behind that of the lower cell in dividing, so that, as in fig. 26, the 

 upper nucleus is in the resting condition while the lower one is in 

 anaphase. Fig. 27 shows the nucleus of the upper cell in meta- 

 phase, which passes to anaphase (fig. 28) and to telophase (fig. 29) 

 while that of the lower cell remains resting. When the filament has 

 reached the 3-celled stage mitosis in the three nuclei proceeds in 

 varying order. In fig. 30 is shown the case in which the nucleus 

 of the basal cell is more advanced, revealing 24 chromosomes in 

 prophase. The following figure shows the nucleus of the terminal 

 cell in advance and now in metaphase. In the next figure the 

 nucleus of the middle cell is already in anaphase. 



At the 4-celled stage of the young gametangium, the nucleus in 

 prophase invariably shows 24 chromosomes (figs. ^$, 34). At about 

 this stage the nucleus in division has almost the same size and 



