Cytology and Movements of the Cyanophycee. 335 
Pate XXYV. 
Fig. 75. . First stage in the formation of the heterocyst of Nostoc. 
Figs. 76-79. Successive stages in the formation of the heterocyst of 
Nostoc. 
Figs. 80-83. Four successive steps in the formation of the net-spireme 
and division of Wollea saccata. 
Figs. 84-86. Different steps in the formation of the spores of Wollea 
saccata. 
Figs. 87-89. Stages in the division of Anabena flos aque. The steps 
follow the order of the letters from a to h inclusive. 
Figs. 90-92. Colonies of Gleocapsa polydermata, showing the cell wall 
surrounding different generations of cells. Evidently here there are 
more laminz laid down after each division than is found in other 
forms. 
Fig. 93. Cells of Nostoc slightly disintegrated, showing the long pro- 
toplasmic connections between the cells. 
Fig. 94. Trichome of Spermosira Kitorea, showing how the sheath is 
formed by the deposition of layers of substance on the inner face of 
the parent walls. As division proceeds, these walls are made to 
hold different numbers of cells, as described in the text. 
