We know that they are directly connected by fibres that arch round through the chiasma.
"Medical Essays" by Oliver Wendell Holmes, Sr.
Chiasma: an X-like crossing of nerve fibers.
"Explanation of Terms Used in Entomology" by John. B. Smith
The nerves are fibrous, and a commencement of the chiasma is certainly present.
"The Works of Francis Maitland Balfour, Volume 1" by Francis Maitland Balfour