Cytology and Movements of the Cyanophycee. 259 
the nucleus and might change from one form to the other. 
By far the most interesting portion of Zukal’s work, how- 
ever, consisted in the finding of very small motile zoospores 
of two sizes, which he called “gametes.” These underwent 
a process of conjugation, a large one uniting with a small 
one, the two surrounding themselves with a common gelati- 
nous envelope, though he was not sure that they fully fused. 
They finally began to divide by cross partitions and then 
grew out into new plants. Both sizes of gamete were 
formed within the protoplasm of the cell, and upon the 
rupture of the cell wall they floated out into the water where 
conjugation occurred (Fig. 65). In 1899 Zukal (103) car- 
ried out additional work on the Cyanophycee, from which 
he concluded that the cyanophycin granules changed to 
slime balls, which in*turn passed to the centre and fused 
into a spider-like body which lay along the partition wall 
between two cells. The substance of the spider-like mass 
was a soluble modification of the granules, and bore about 
the relation to them that grape sugar does to starch. It 
travelled from cell to cell through pores in the partition 
walls in order that it might increase at certain points, as in 
the akinetes. In 1894, in his work (101) on Oscillaria, he 
considered that the colored crust layer was a chromato- 
phore. The vacuoles, especially in the hair-like ends of the 
Rivulariacee where they appeared regularly, he thought to 
be signs of degeneration. He also thought the central sub- 
stance to be identical with the slime balls of Palla. 
If Zukal’s contentions are correct, it would seem that the 
three negative characteristics of the Cyanophycee, 1. e., lack 
of nucleus, lack of chromatophore and lack of sexuality, 
have all been proven to be erroneous. However the possi- 
bilities of making such observations seem quite improbable, 
especially in living material arranged in “hanging drop” cul- 
tures as he used. It is quite impossible to use the exceed- 
ingly high powers of the microscope that are required to 
show the structure and conjugating gametes on account of 
