ALGiE. 153 



rapid, being completed in one night and the next 

 morning. The second active generation thus formed 

 resembles the first, except that the active cells are 

 green from the first, and have a smaller red nucleus 

 in the interior. The subsequent active generations 

 bear a general resemblance to the preceding, but 

 with many modifications. For example, the full- 

 grown swarm cells not unfrequently assume strange 

 two-lobed or four-lobed shapes, beginning to divide 

 before they come to rest, or sometimes a transverse 

 constriction and bisection of the cell takes place. 

 The formation of vacuoles is a pretty constant 

 phenomenon in the later active generations, and 

 there may be many of them excentrically placed, 

 with the red nucleus retaining its central position, 

 or a single central vacuole, causing a lateral displace- 

 ment of the red nucleus. The red nucleus often 

 becomes very small in the last generations, so that 

 it resembles the red corpuscle which Ehrenberg 

 called "eye-spot." 



Not uncommonly the red colour wholly disappears. 

 In the later stages of the " cycle of generations " the 

 formation of microgonidia takes place. Many in- 

 dividuals, instead of producing four daughter-cells, 

 undergo further division, so as to produce a brood 

 of sixteen or thirty-two minute cells, which at first 

 form a mulberry-like body, at length separating to 

 commence a very active swarming inside the parent 

 cell, which ends in a rupture of the envelope, and 

 the dispersion of the little swarmers. These are of 

 a more elongated shape than the large swarmers, of 

 a yellowish or dirty yellowish green colour, with 



