from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An inward fold on the surface of the embryonic ectoderm that develops into part of the anal passage.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The back ectodermal part of an alimentary canal.
from The Century Dictionary and Cyclopedia
- n. See proctodæum.
This invagination is termed the proctodeum, and it meets with the entoderm of the hind-gut and forms with it the anal membrane.