52 COCCOPHYCEE. 
cells sink to the bottom, or attach themselves to the sides. The transi- 
tion from one active generation to another takes place through a transi- 
tory resting generation of extremely short duration. The full-grown 
swarming cells finally come to rest within their wide shirt-like envelope, 
and almost simultaneously divide into two cells, which, without becom- 
ing active, divide again into two cells. Thus within the mother enve- 
lope are produced four daughter-cells (more properly grand-children), 
which begin to move soon after they are completely formed, and, tearing 
open the delicate enveloping vesicle, part company. The whole of this 
process of development is gone through very rapidly, being completed 
in one night and the succeeding morning. The second active generation, 
thus formed, resembles the first, with the single distinction 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 resem- 
blance to the preceding, but many modifications present themselves. 
Thus, for example, we not unfrequently see the full-grown swarm-cells 
assume strange two-lobed, or even four-lobed, shapes, beginning to 
divide before they come to rest ; or sometimes a transverse constriction 
and bisection of the cell takes place, caused by a partial protrusion of 
it from the loose shirt, &c. The formation of vacuoles is a pretty con- 
stant phenomenon in the later active generations, and there may be 
several of them eccentrically placed, with the red nucleus retaining its 
central position, or a single central vacuole, causing a lateral displace- 
ment of the red nucleus. This red nucleus often becomes very small 
in the last generations, so that it very much resembles, especially when 
rendered parietal by the formation of a central vacuole, the red cor- 
puscle occurring in the gonidia of many genera of Algw belonging to 
very diverse families, and which was called the ‘eye’ in the Volvo- 
cinee by Ehrenberg. 
“A total disappearance of the red colour not unfrequently occurs. 
In the later stages of the cycle of generations arrives, finally, the for- 
mation of microgonidia; many individuals, instead of producing four 
daughter-cells, undergo further division, so as to give birth to a brood 
of 16 or 32 minute cells, which, before they separate, form a mulberry- 
like body, but separating at length, commence a very active swarming 
inside the parent envelope, terminating in the rupture of this coat and 
the rapid dispersion of the little ‘swarmers.’ These are of longer 
shape than the large ‘ swarmers,’ only about ‘0066, rarely ‘01 mm. long, 
of yellowish or dirty yellowish green colour, with reddish ciliated 
points. They do not exhibit increase of size, like the large ‘ swarmers,’ 
never become coated with a perceptible and loose membrane, and have 
no further power of propagation. Most of them die after they have 
settled to rest, dissolving away; others turn into little red globules, and 
it is doubtful whether they can grow up to the normal size. If we now 
further examine how the cycle of active generations is closed and 
carried over tothe resting vegetation, we find that the large ‘ swarmers’ 
of the last active generation, when their growth is completed and they 
have attained the stage of rest, instead of dividing again remain un- 
divided, assume a perfectly globular form, and in the course of a few 
days become clothed by a thick, closely applied cell membrane, while 
the earlier loose distant membrane gradually disappears. The contents, 
which at the commencement of the rest were all green, except the little 
red nucleus, or even often entirely green, now gradually become red 
again, passing from green through many tints of brown, or of brilliant 
golden green and golden brown, into red. These globular, thick-coated 
cells (the same as those with which we began) behave like seed-cells 
or spores, passing into a state of perfect vest. They do not exhibit any 
growth, and after the membrane has attained its proper thickness, and 
