Hydrodictyon utriculatum . 635 
Fig. 21. Vertical section, showing two pyrenoids of unequal size in the same 
cell. The larger pyrenoid in resting stage; smaller showing starch-formation. 
X 2250. 
Figs. 22-25. Disappearance of starch and pyrenoids prior to spore-formation. 
X 2250. 
Fig. 26. Portion of vertical section, showing distribution of nuclei, pyrenoids, 
and starch grains in the protoplast, x 600. 
Fig. 27. A pyrenoid and two nuclei lying very close together. Nuclei are 
in prophases of division. Pyrenoid surrounded by homogeneous substance formed 
by solution of starch, x 2250. 
Fig. 28. Early stage of spore-formation, showing a single pyrenoid remaining 
in the protoplasm, x 600. 
Fig. 29. Young swarm-spores containing starch -grains, x 1500. 
Fig. 30. Young cells, each containing a pyrenoid and several starch-grains. 
X 1500. 
Fig. 31. Pyrenoid showing unusual forms of starch-grains. 
