REJUVENESCENCE IN NATURE. 303 



microgonidia, added on to one another in this way, 

 amount to six or seven, which indicates a five- to six-fold 

 repetition of the division in the descending order. The 

 formation of the globular or ellipsoidal expanding mother- 

 cell of the spore of Bulboclicetc is peculiar, and deviates 

 somewhat from the similar process in (Edogonium. The 

 spore-bearing cell (the sporangium) usually presents itself 

 in this genus as a branch at the upper margin of a stem- 

 cell, and mostly as the first (more rarely the second) cell 

 of the branch, surmounted by a small bristle-bearing cell, 

 or even by two cells, one narrowly tubular, and filled 

 sparingly with green contents, on which the second, 

 hyaline and bristle-bearing, is seated like a little lid. The 

 origin of the branch becoming developed into a sporan- 

 gium, takes place, as in Cladophora, through formation 

 of a bagging out process at the upper margin of the stem- 

 cell. Into this protruded sac the densely-fluid, green con- 

 tents of the stem-cell (containing starch-granules) gradu- 

 ally travel, and this in two portions. In the first place 

 merely the lower half of the stem-cell loses its coloured 

 contents, and then it is shut off from the upper, still 

 green half, by a delicate horizontal partition ; soon, how- 

 ever, since the protruded sac, not yet shut off from the 

 stem-cell, continues to grow and to expand toward a 

 globular form, the green contents travel out of the upper 

 half of the stem-cell, into the sac-like branch, after which 

 the partition is formed between this and the stem-cell. 

 The stem-cell bearing the sporangium often appears per- 

 fectly hyaline after this process, and always divided in 

 the middle by a horizontal septum, a division which 

 never occurs in the other stem-cells. Only as an excep- 

 tion have I seen stem-cells more or less densely filled 

 with green contents, notwithstanding that they bore a 

 sporangium at the upper margin ; the division of the 

 cell did not exist in this case. The formation of the one 

 to two little cells beside the bristle, at the tip of the 

 sporangium, does not take place until after the protruded 

 sac is shut off from the stem-cell. From this sketch of 



