334 Phillips on a Comparative Study of the 



Fig. 40. Same as Figs. 38 and 39, but showing the cilia massed down 



by the action of the reagents. 

 Fig. 41. Portion of filament of Oscillaria showing cross lines on the 



cell walls. 

 Fig. 42. Portion of filament of Oscillaria showing longitudinal lines 



on the cell walls. 

 Figs. 43-44. Portions of filaments of Oscillaria in which the end cells 



have been pressed away from the second cells, exposing minute 



protoplasmic threads connecting the protoplasts. 

 Fig. 45. Growth of a spore of Oscillaria. The old spore wall or exo- 



sporium still remains. 

 Figs. 46-50. Development of a peculiar amoeboid-like spore and its 



formation of a new Oscillaria trichome. See page 304. 

 Figs. 51-52. Formation of spores by the fusion of the cells. The 



darker cells act as "nurse cells" to feed the spore-forming cells. 



The successive stages are lettered from a to h. 



Plate XXIV. 



Fig- 53- Full-grown trichome of Cylindrospermum, showing cilia and 

 hair-like appendages. 



Fig. 54. Cross-section of spore of Cylindrospermum. 



Fig. 55- Full-grown spore of Cylindrospermum before withdrawal of 

 appendages. 



Fig. 56. Double heterocyst in Cylindrospermum. Shows the gelatinous 

 envelope frayed out into finger-like processes at the end. 



Figs. 57-62. Successive stages in the formation of the spores of Cylin^ 

 drospermum. 



Fig. 63. Spore of Cylindrospermum treated with iodine and sulphuric 

 acid, showing the plasmolized protoplast with the finger-like pro- 

 cesses which passed out through the spore walls. 



Fig. 64. Trichome of Cylindrospermum in which a second spore has 

 formed. 



Fig. 65. Copy of Zukal's figure, which shows hair-like flagella from 

 the partition walls of Cylindrospermum. The different sized bodies 

 crushed out of the cell are what he terms gametes. 



Figs. 66-73. Successive stages in the karyokinetic division of Cylindro- 

 spermum. 



Fig. 74. Highly magnified end of trichome of Cylindrospermum, show- 

 ing the spore and heterocyst with their long finger-like processes 

 and the gelatinous sheath frayed out into shreds. The pores 

 through which the protoplasm passes to connect the protoplasts are 

 also shown. 



