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of Valonia. If this is the case, Schmitz' description of the evo- 

 lution of the thallus can agree better with the real condition in 

 this plant. 



Whilst, as mentioned above , I have not succeeded in finding 

 any trace of zoospore-formation in D. favulosa, I have been so for- 

 tunate as to find a specimen of D. van Bosseœ, whose cells without 

 any doubt were about to form zoospores (Fig. 9). 



Whilst in the normal vegetative cells the chromatophores with 

 pyrenoids and nuclei form a net-work in the wall-plasma, in those 

 in question the cell contents were aggregated into irregularly 

 formed bodies consisting of a larger broad plate with or without 



Fig. 9. Dictyosphœria van Bosseœ n. sp. 



Cells in zoospore-formation, (ca. 20 : 1). 



holes in the middle of the cell, from which narrower prolongations 

 ran down along the sides of the cells, giving them a very charac- 

 teristic appearance. And that it really is the formation of the 

 zoospores we have to do with was furthermore made evident by 

 the fact, that in the cell wall of some of the cells 2—4 holes 

 were found, through which the zoospores could escape. 



The cell contents have a very great likeness to what is found 

 in the above-mentioned species. With regard to the hapteræ along 

 the edges of the cells I may refer to Miss Crosby's description 

 and figures with which they show a great likeness, though on the 

 other hand they are not so regularly arranged and also differ some- 

 what in shape from those in D. favulosa. 



