cells sink to the bottom, or attach themselves to the sides. The transition
from one active generation to another takes place through a transitory
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 becoming
active, divide again into two cells. Thus within the mother envelope
are produced four daughter-oells (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 vei-y 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 iu
the interior. The subsequent active generations bear a general resemblance
to the preceding, but many modifications present themselves.
Thus, for example, we not unfreqnently see the full-grown swarm-oells
assume strange two-lobed, or even four-lobed, shapes, beginning to
divide before they come to r e s t; or sometimes a transverse constriction
and bisection of the cell takes place, caused by a partial protrusion of
it from the loose shirt, &o. The formation of vacuoles is a pretty constant
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 corpuscle
occurring in the gonidia of many genera of Algm belonging to
very diverse families, and which was called the ‘ eye ’ in the Vohv.
cmra by Ehrenherg.
“ A total disappearance of the red colonr not unfreqnently occurs.
In the later stages of the cycle of generations arrives, finally, the formation
of microgonidia; many individuals, instead of producing four
daughter-oells, undergo further division, so as to give birth to a brood
of 16 or 32 minute cells, which, before they separate, form a mulberrylike
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 to the 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 undivided,
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 nnoleus, or even often entirely green, now gradually heoome 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-oells
or spores, passing into a state of perfect rest. They do not exhibit any
growth, and after the membrane has attained its proper thickness, and
the contents their red colour, no further visible alteration takes place
so long as they are kept in water. A dessioation must take place before
a new°oycle of generations can begin. Perfectly dry specimens placed
again in water ordinarily prodnoe active gonidia the next morning.
Original specimens obtained in 1841 had retained their vital force during
a preservation of seven years in a herbarium.
“ In order to complete the main features of the picture of the alternating
generations of this multiform creature, I must notice that, in
addiWon to the described active generations (macrogonidia and microgonidia)
and the concluding generation, passing into the spore-like condition
of rest, there are other generations which, as compared with tho
gonidium-like and spore-like couditions, must he regarded as the proper
representatives of the vegetative development. These are generations
endowed with quiet and slow vegetative growth, which multiply by pure
vegetative division, unaooompanied by any swarming movement. It
depends solely upon external conditions whether the resting cells, which
are here characterized as seed-oells (spores), at once give rise to the new
active generations, or to a series of quietly vegetating generations of
cells. The former is the case when the seed-oells are totally immersed
in water, the latter when they occur on a spot which is at once damp
and exposed to tho air, as is the case in the native condition, espeoia,lly
in the milder intervals of winter, and in the damp season of approaching
spring, but temporarily also at all other seasons, on the margins of the
little basins inhabited by Chlamydococcus, as often as they are filled by
showers of rain. In cultivation iu the house these vegetative generations
are rarely observed, while in their native stations they certainly
occupy the most important place in the alternations of the various conditions
of life, as may be concluded from the thickness of the crusts
and membranes formed by such vegetative multiplication. The formation
and multiplication of these vegetative generations also take place
by the division of the cell contents, either by simple division, the first
generation being transitory, or by double halving (apparently quartering).
But the newly formed cells do not slip out, like the young
‘ swarmers,’ from the mother envelope ; they remain in the same place
and position. The membrane of the rnother-cell appears to become
softened, expands, and becomes gradually drawn out to nothing, rather
than regularly burst open ; it at length vanishes iu some undistinguish-
able way, the daughter-oells meanwhile acquiring a tolerably thick,
closely applied cell membrane of their own. The division is repeated
many times in this way, and as the cells all remain in intimate contact,
first small families, but by degrees large conglomerates of cells are pro-
duced. The size of the single cells in these groups varies from '01 to
•02 mm. ; their shape is not truly globular, but partly bounded by flat
surfaces, as results from the alternating divisions, according to the three
directions of space. Ordinarily the colour is light brown. If ignorant
of the rest of its history, one would be led by the form and mode of
division of the cells to regard these crusts as belonging to a Pleurococcus.
In the same crusts occur isolated large cells, loosened from
their connection with the others, perfectly globular in form, and appearing
to divide no more, but to have passed again into the condition of
resting spore cells. Tney are distinguished from the rest by their
darker contents and thicker cell membrane. Probably the return of
these to renewed resting vegetation takes place by a passage through
the series of active generations. Every shower of rain will wash away
these loose ripe cells of the crusts of Chlamydococcus; carried into
collections of rain water, they will soon produce the active brood, which,
returniug to rest after a few active generations, settles on the margins
of the little puddles, and then recurs to the resting mode of vegetative
inuitiplication.”
I