Meanwhile, inside a turtle egg…

Antenna-like cell appendage may help turtle embryos sense sex-deciding nest temperatures phys.org

A turtle's sex is decided by how warm the sand around the egg is, and nobody could say what inside the embryo was doing the measuring. Researchers have now found the likely thermometer: an antenna-like appendage on embryonic cells that responds to a difference of a degree or two and steers development toward male or female.