Gastrula Definition

Gastrula Sentence 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.

• It has usually been regarded as representing both endoderm and mesoderm, and the groove which usually leads to its formation has been compared to the abnormally elongated blastopore of a typical gastrula.

• To the primitive two-cell-layered form, the hypothetical ancestor of all Metazoa or Enterozoa, Haeckel gave the name Gastraea; the em- bryonic form which represents in the individual growth from the egg this ancestral condition he called a " gastrula."

• The term " diblastula " was subsequently adopted in England for the gastrula of Haeckel.

• 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.