This cup-shaped embryo is called the gastrula.
"The Whence and the Whither of Man" by John Mason Tyler
The gastrula stage was the palingenetic repetition of the ancestral form of all Metazoa, the Gastraea.
"Form and Function" by E. S. (Edward Stuart) Russell
With what lower type has the gastrula been compared?
"Text Book of Biology, Part 1: Vertebrata" by H. G. Wells
Gastrula: that embryonic stage resembling a sac, with an outer layer of epiblastic cells and an inner layer of hypoblastic cells.
"Explanation of Terms Used in Entomology" by John. B. Smith
The segmentation is complete; one side of the hollow blastosphere invaginates and forms a gastrula.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7" by Various
Is there any considerable difference between the size of the egg and the size of the blastula and gastrula?
"A Guide for the Study of Animals" by Worrallo Whitney
The embryo in this stage is known as a gastrula.
"The Biological Problem of To-day" by Oscar Hertwig
A gastrula is established by a mixed process of embole and epibole.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7" by Various
The development of the Lancelet presents us with an instance of the two-layered larva, or Gastrula.
"Stories of the Universe: Animal Life" by B. Lindsay
From the gastrula type the higher subdivisions of animal life probably diverged, as separate branches from a common trunk.
"The Elements of Geology" by William Harmon Norton