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Phylum Thallophyta - The Algae - Chlorophycae - Volvocales - Pandorina
The colony consists of sixteen cells, each like a single Chlamydomonas cell. The cells are rather pyramidal in shape and are arranged in an oval group with their pointed ends inwards. They are closely packed together, and the whole coenobium is surrounded by a mucous investment.
Each individual cell has two widely divergent flagella, by means of which the whole colony is propelled along, generally with a definite anterior end, in the cells of which the eye-spots are larger and better developed.
Reproduction in Pandorina
Reproduction is both sexual and asexual. Asexual reproduction consists in the formation of daughter colonies within the cells of the parent.
Each cell divides into sixteen cells, which at first form a curved plate. This later becomes flat and then curves in the reverse direction, the corners meeting to form a hollow coenobium. This is liberated as a new colony after the breakdown of the parent cell. This inversion of the daughter colonies during development should be compared with that in Eudorina and Volvox. The liberation of independent zoospores rarely occurs.
Sexual reproduction consists in the liberation of the naked protoplasts of the cells, which escape from the membranes and become the gametes. Conjugation is usually isogamous, but there is a tendency towards a preferential fusion of gametes of unequal size, thus showing an adyance to\yards anisogamy, which becomes much more pronounced in Eudorina and Volvox.
The zygote germinates to liberate a single zoospore, ,yhich divides to form a new colony. Four cells are actually formed by the germinating zygote, but only one of these survives to form a zoospore, while the other three abort. This suggests that meiosis probably occurs at this stage, as in Gnium.
The colony consists of sixteen cells, each like a single Chlamydomonas cell. The cells are rather pyramidal in shape and are arranged in an oval group with their pointed ends inwards. They are closely packed together, and the whole coenobium is surrounded by a mucous investment.
Each individual cell has two widely divergent flagella, by means of which the whole colony is propelled along, generally with a definite anterior end, in the cells of which the eye-spots are larger and better developed.
Reproduction in Pandorina
Reproduction is both sexual and asexual. Asexual reproduction consists in the formation of daughter colonies within the cells of the parent.
Each cell divides into sixteen cells, which at first form a curved plate. This later becomes flat and then curves in the reverse direction, the corners meeting to form a hollow coenobium. This is liberated as a new colony after the breakdown of the parent cell. This inversion of the daughter colonies during development should be compared with that in Eudorina and Volvox. The liberation of independent zoospores rarely occurs.
Sexual reproduction consists in the liberation of the naked protoplasts of the cells, which escape from the membranes and become the gametes. Conjugation is usually isogamous, but there is a tendency towards a preferential fusion of gametes of unequal size, thus showing an adyance to\yards anisogamy, which becomes much more pronounced in Eudorina and Volvox.
The zygote germinates to liberate a single zoospore, ,yhich divides to form a new colony. Four cells are actually formed by the germinating zygote, but only one of these survives to form a zoospore, while the other three abort. This suggests that meiosis probably occurs at this stage, as in Gnium.
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