380 Spratt . — Observations on Life-history of Anabaena Cycadeae. 
Fig. 9. Vegetative cells in the process of division ; a = typical cell; b — constriction in invest- 
ment just appearing ; c = division of central body ; d = complete division of contents ; e = membranes 
completed and two cells formed. 
Fig. 10. Filament in which heterocysts are developing. 
Fig. 11. Filament containing terminal and intercalary heterocysts in which the thickening of 
the membranes has commenced. 
Fig. 12. Filament in which the heterocysts have developed the lip-like prominences (/.), and 
the contents ( c.c .) have contracted. 
Fig. 13. Detached heterocyst. 
Fig. 14. Development of a new heterocyst on either side of an old one which is consequently 
liberated. 
Fig. 15. Development of new heterocysts following the excretion of intercellular substance (s.). 
Fig. 16. Filament showing the development of spores (sp.'). 
Fig. 1 7, a-f. Series of stages illustrating the first type of spore germination. 
Fig. 1 8 , a- c. Series illustrating the second type of germination ; piece of spore wall split off. 
Fig. 19. Spore germinating. Piece of wall remains attached. 
Fig. 20. Third type of germination. 
Fig. 21, a-c. Fourth type; w ., new membrane dividing spore contents ; p., pore. 
Fig. 22. Heterocyst in first stage of gonidia formation ; i.m., new internal membrane. 
Fig. 23. Contents of heterocysts divided into two in (a) and three in ( b ). 
Fig. 24. Three gonidia being liberated. 
Fig. 25. Formation of number of gonidia (g) ; a — beginning of their liberation; b — liberation 
continued ; c •- structure of gonidia visible. 
Fig. 26. Gonidium germinated to form a small filament. 
