noun. The opening of the archenteron.

noun. In embryology, the aperture of invagination of a blastula or vesicular morula which has become a gastrula; the orifice of an archenteron; the primitive combined mouth and anus of a gastræa-form; an archæostoma. See cut under gastrulation.

noun. The pore or opening leading into the cavity of invagination, or archenteron.

noun. The opening into the archenteron.

noun. the opening into the archenteron

"This feeling of frustration, so incisively conveyed by these considerations by P. Medawar, pervaded in the forties the field of experimental embryology which had been enthusiastically acclaimed in the mid-thirties, when the upper lip of the amphibian blastopore brought this area of research to the forefront of the biological stage."

blastoporal  blastoporic  

opening  orifice  porta