How to use Blastula in a sentence

blastula
  • Then follows the phenomenon of gastrulation, by which onehalf of the blastula is invaginated into the other, so as to obliterate the segmentation cavity.

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  • 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.

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  • When the blastula is oval and freeswimming the inner mass is formed by unipolar immigration from the hinder pole.

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  • 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.

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

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  • 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.

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

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