474 Smith. — Cytological Studies in the Protococcales. IT. 
a colony shows 16-nucleate cells adjacent to 2 - and 4-nucleate ones (Text- 
fig. 4). There are two general types of nuclear behaviour previous to 
spore formation in Algae and Fungi : either a succession of nuclear divisions 
of a single large nucleus in a mature cell, or nuclear division as the cell grows, 
resulting in a multinucleate condition when mature. In the latter case there 
is no nuclear division just previous to spore formation. The former method 
is followed by Synchytrium and Ulothrix ; Rhizopus , Chavacium , and 
Text-fig. 3. Outline drawings, at three-minute intervals, of the changes taking place in the first 
few minutes after the cessation of zoospore movement. In this colony the swarming lasted eight 
minutes, and the first drawing was made fifteen seconds after the motion ceased. ( x 2,000.) 
Hydrodictyon follow the latter. In P ediastrum there is a combination of the 
two types, inasmuch as the cell is multinucleate, but just before zoospore 
formation a period of active nuclear division sets in, the resulting nuclei 
lying a short distance from one another within the cytoplasm. At times 
there is a grouping of the nuclei into fours (Figs. 11, 19), but at other times 
this grouping is not apparent (Fig. 9). The grouping of the nuclei in fours 
and eights has been observed in Hydrodictyon by Timberlake ( 17 ), so that 
