1912] YAMANOUCHI—CUTLERIA 467 



double (fig. 148) on the dorsal surface, and between the dorsal 

 and ventral superficial layers there are two or three layers of 

 parenchyma-like cells of huge size. Any cells in the superficial 

 layer of the dorsal surface of young Aglaozonia are favorable for 

 studying vegetative mitosis. 



The vegetative mitosis was studied chiefly in the nucleus of the 

 superficial cells of Aglaozonia. The main features of the divisi on 

 are similar to those of Cutleria, and consequently a detailed account 

 and figures will be omitted at this time, but a few points should be 

 noted. 



The size of the nucleus in the superficial cells is either about the 

 same as that of the plastids within the cell or is even smaller. 

 When the nucleus is in the resting state, the chromatin network is 

 remarkably similar to that of Cutleria, the chromatin knots being a 

 conspicuous feature, though few in number, while the fibrils are 

 very scanty and broken. One noteworthy feature not common in 

 the case of Cutleria, but of general occurrence in Aglaozonia, is that 

 deeply stained granules about the size of the chromatin knots 

 within the nucleus are present around and close to the membrane 

 outside the nucleus. These granules become faintly stained and 

 evidently diminished in size during the mitotic phase within the 

 nucleus, and they entirely disappear while the nucleus is still in 

 prophase. It seems probable that the granules may be material 

 allied to chromatin that might have passed into the nucleus, thus 

 contributing to the formation of chromosomes. 



The chromosomes appearing in prophase are 48 in number, and 

 their form is in nothing different from those of Cutleria. 



FORMATION OF ZOOSPORANGIA 



Zoosporangia are produced on the upper surface of the thallus. 



When 



from above, the 



sporangia are distinguished by patches of darker color, contrast- 

 ing sharply with the light brownish olive color of the sterile 



portion. 



of thousands 



zoosporangia which are produced in palisade arrangement upon 



the thallus. The details of the origin of the : 



oosporangium 



follows: a superficial cell of the thallus elongates slightly and 



