Noun:

சிற்றரும்பர்,

blastula's Usage Examples:

If the embryo is set free as a free-swimming, so-called planula-larva, in the blastula, parenchymula, or gastrula stage, then a free actinula stage is not found; if, on the other hand, a free actinula occurs, then there is no free planula stage.

at one pole only, and in a connected layer with orderly arrangement, so that the gastrula stage is reached at once from the blastula without any intervening parenchymula stage.

It has simply been traced as far as the formation of a diblastula which acquires a ciliated band, and becomes a nearly spherical trochosphere.

C, Diblastula of an Opisthobranch (Polycera) with elongated blastopore oi.

The result of cleavage in all cases is a typical blastula, which when set free becomes oval and develops a flagellum to each cell, but when not set free, it remains spherical in form and has no flagella.

Thus a planula larva may be a blastula, or but slightly advanced beyond this stage, or it may be (and most usually is) a parenchymula; or in some cases (Scyphomedusae) it may be a gastrula.

As in other Molluscan groups, we find a wide variation in the early process of the formation of the first embryonic cells, and their arrangement as a diblastula, dependent on the greater or less amount of food-yolk which is present in the egg-cell when it commences its embryonic changes.

'This is the blastula stage occurring universally in all Metazoa, probably representing an ancestral Protozoan colony in phylogeny.

This is the blastula stage occurring universally in all Metazoa, probably representing an ancestral Protozoan colony in phylogeny.

The tracing of the exact mode of development, cell by cell, of the diblastula, the coelom, and the various tissues of examples of all classes of animals was in later years pursued with immense activity and increasing instrumental facilities.

When the blastula is spherical and not set free, the germ-layer formation is always multipolar, either by immigration or by delamination, i.

The segmentation or cleavage of the ovum which follows � upon fertilization terminates in the achievement of the blastula form, a minute sphere of cells surrounding a central cavity.

Some form their diblastula by emboly, others by epiboly; and in the later history of the further development of the enclosed cells (archenteron) very marked variations occur in closely-allied forms, due to the influence of a greater or less abundance of food-material mixed with the protoplasm of the egg.