Cytology and Movements of the Cyanophycece. 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 Cyanophycese, 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 (loi) on Oscillaria, he 

 considered that the colored crust layer was a chromato- 

 phore. The vacuoles, especially in the hair-like ends of the 

 Rivulariaceje 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 Cyanophyceae, i. 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 



