archaeostomatous

from The Century Dictionary.

• Pertaining to or having the characters of the Archæostomata.
• In biology, having a primitive blastopore or original orifice of invagination of a blastosphere which has undergone gastrulation; retaining an archenteric aperture, as distinguished from any other which may be acquired by a deuterostomatous gastrula: it is the usual state of those gastrulæ which are formed by emboly.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Biol.) Applied to a gastrula when the blastopore does not entirely close up.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective biology Applied to a gastrula when the blastopore does not entirely open up.