The title is Latin for "by hand."
This is the first appearance in the series of Adam Baldwin playing John Doggett's friend, Knowle Rohrer. Baldwin had originally auditioned for the part of Doggett.
Scully and another character have a final showdown at a facility called Walden-Freedman Army Research Hospital. Walden Freedman is a professor at Humboldt State University in California. He teaches mathematics.
The production code is #8ABX08.