PROTOCOCCTJS PLUVIAIJS. 529 



The term chlorophyll- vesicle (chlorophyll-blaschen) wns 

 first introduced into the anatomy of the Algse by Niigeli, 

 although Meyen had previously expressed a similar view 

 respecting the structure of the chlorophyll. Nageli 

 regards them as minute membranous vesicles, containing 

 a mucus coloured with chlorophyll, only apparently pre- 

 senting the aspect of nuclei or hollow spaces, frequently 

 forming starch in their interior, and which are found in tiie 

 Palmellaceee, DesmidicEe, Vaucheriacese, and piulticellular 

 Algae. In Trot, pluvialis, they present the appearance of 

 minute green rings, about 0-002'" in diameter, the in- 

 terior being sometimes darker, sometimes more clear, and 

 frequently almost opaque. They occur principally in the 

 green cells, to the number of one, two, three, four, or 

 more. Rarely observed in the red cells. They are 

 coloured dark brown or violet, by iodine. The author 

 supposed that in Protococcus they stood in connexion 

 with the division of the cell; but could not determine 

 with certainty that their number corresponded with that 

 of the secondary cells. Kiitzing looked upon them as 

 gonidia or cell-nuclei, assigning to them the function of 

 propagation of the individual; but Cohn does not coin- 

 cide in this view, though ignorant of their true nature 

 with respect to the life of the cell. 



The sometimes colourless, sometimes green granules, 

 are very minute, none being more than O'OOl'" in size. 

 The colourless may be regarded as protoplasma- (mucus, 

 schleim-) granules, the green as chlorophyll granules, 

 which latter must not be confounded with the chlorophyll 

 vesicles. 



Whether there be a true cell-nucleus in Protococcus, 

 Cohn has not ascertained with complete certainty. It is 

 known, moreover, that in most of the other Algse, and par- 

 ticularly the unicellular, it has not yet been made out 

 satisfactorily, whether, in the first place, a nucleus does 

 occur, and if it does, what its function may be. 



The presence of starch has above been stated to be 

 doubtful. 



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