Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
All images are the dorsal view with anterior pointing up.S14L: Late stage14; S17M: Middle stage 17; S19E: Early stage 19; Scale bars, 200 µm in (A–L) and 500 µm in (M–X).
