326 Phillips on a Comparative Study of the 
nucleus radiate out toward the periphery of the cell, piercing 
the chromatophore and cell wall, and project in the form of 
the cilia which cause the movements of the trichomes. 
11. The finger-like processes upon the end cells of Oscil- 
larva, and those surrounding the heterocysts and spores of 
Cylindrospermum, are not parasitic, but definite organs of 
the cell, having a motion of their own. They apparently 
assist the trichomes to pass around obstacles. 
12. The protoplasts of the cells of filamentous Cyano- 
phycez are all connected by fine protoplasmic threads which 
pass through communicating pores in the walls. There is 
usually one central pore, though other finer pores and 
threads may be present. 
13. The heterocyst is a modified vegetative cell which 
gradually fills with some substance, passed to it from the 
other cells, through the pores for the protoplasmic threads 
which connect it with the other cells of the trichome. This 
substance finally fills the whole of the heterocyst. It gives 
some of the reactions for chromatin and may be a modifica- 
tion of that substance. The heterocyst of Cylindrospermum 
will develop into a spore if it gets sufficient nutriment and 
hereditary material passed into it from the other cells. 
14. Spores are formed in Oscillaria from groups of cells, 
usually two, but it may be one, three or four. These fuse 
by the absorption of their partition walls. The growth of 
the spore is effected by substances passed into it from the 
other cells. The spores of Cylindrospermum are formed 
from a single cell which divides, the end cell becoming a 
heterocyst and the second cell the spore. It also receives 
substances from the other vegetative cells. 
15. The cell wall is composed of cellulose in its earlier 
stages, but later becomes impregnated with or modified into 
some substance akin to fungus cellulose. 
16. The cell wall is laid down as microsomata, in lamellz 
on the inside of the cell wall. One such lamina is laid down 
at each division. Thus every succeeding lamina from within 
