ARE THE DESMIDS AND DIATOMS SIMPLE CELLS ? 
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chrome. The nucleus , n , with its nucleolus , occupied a posi- 
tion at the central part of the frond, where the ends of the 
dark band of endochrome, //, are seen impinging against it; 
the usual terminal vesicle, v, being present near the apex of each 
horn of the cellulose crescent. The rupture of the frond took 
place (as it almost invariably does) at the centre of the convex 
part; and, at this point, its contents slowly exuded into the 
water on the slide. Simultaneously with this exudation an 
Fig. 2. 
A. Frond of Closteriura in which division has already commenced — a, cellulose 
wall ; n, nucleus resting in the midst of the colourless protoplasm ; e, endo- 
chrome; m, investing membrane of endochrome; v v, vesicles containing 
vibratile granules ; //, “fillets.” 
B. Crushed frond of a specimen of the same ; a, cellulose wall ; e, endochrome 
now become slightly granular ; c jp, globules of colourless protoplasm ; n, 
nucleus ; v v, vesicles. 
entering current of water became distinguishable by the minute 
particles of foreign matter which were carried in along with it ; 
and the amorphous colourless protoplasm at once broke up into 
a number of subglobular masses (b, c jp ) ; the periphery of 
each of which presented just as close a resemblance to a cell- 
membrane as the periphery of the sinuous, but still unbroken, 
