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460 MR, O. MASSEE ON THE LIFE-HISTORY 



enclosed in the mucilage secreted by the unsegmented mother-cell. 

 There is a total absence of septa, and the cell now resembles a 

 pair of dumb-bells crossing in planes at right angles to each 

 other, and enclosed in a hyaline sphere of mucilage. 



"When the above-described stage of development has been 

 reached, each of the four swollen apices becomes segmented into 

 four portions ; but this process differs from the method described 

 as taking place in the mother-cell, in the segmentation into four 

 lobes not being simultaneous. In the first instance, each swollen t4 

 apical portion is divided by a cell-wall lying in the same plane 

 as the long axis of its stem ; the two segments diverge, e 

 becoming stipitate, the stem-like portions starting from the apex 

 of the original stem and forming a dichotomy. When the stems 

 supporting the two segments have attained a length of about 8/i, 

 their swollen chlorophyllose apices again divide into two equal 

 portions, by septa developed in a plane at right angles to those 

 of the previous generation ; the stems continue to increase in 

 length and diverge as before, forming a second dichotomy. I f 

 each of the first four segments has divided into four portions, 

 the cell now consists of sixteen globose chlorophyllose portions 

 terminating an equal number of hyaline stem-like achlorophyllose 

 threads radiating equally in all directions from a central starting- 



ach 



arms 



in turn giving origin to two others by a second bifurcation, the 

 ultimate arms bearing at their free tips the chlorophyllose 

 portions of the cell. The third time of division sometimes 

 terminates the vegetative activity of the cell, but usually the 

 segments divide in a similar manner four or five times, so that 

 the cell consists respectively of thirty-two or sixty-four segments. 

 As a rule all the swollen apices divide into two segments each, in 

 rare instances three are produced, or no segmentation takes place, 

 when the geometrical symmetry of the cell is disturbed and a 

 departure from the typical sphere results. At the period of 

 segmentation of any given generation of swollen tips, the mucila- 

 ginous cell-wall surrounding each loses its individuality, »» 

 mingles with the general sphere of mucilage surrounding the 

 complex cell. 



^ The vegetative phase terminates abruptly, and is ^ once 

 followed by that connected with reproduction. The chloro- 

 phyllose masses of protoplasm terminating the ultimate dicb°- 

 toines become slightly contracted, at the same time 



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