How do I enable SSH from a wifi to a desktop coected by an Ethernet cable (Ubuntu 15.10)?

I have a laptop and a desktop (both ruing linux ubuntu 15.10). I work mainly on the desktop, but sometimes I like to be around the house with the laptop.

Right now, I have ssh working so that, when the laptop is coected via etheet, I can work on my desktop from the laptop.

However, I caot see the desktop at all from the wi-fi coection. All I've got is the arp-scan --localnet command; I haven't been able to find any other scans.

I believe everything--the etheet and wifi--is routed by the same router (netgear) but I guess, now that I think about it, that probably isn't true. How do I get access to the desktop via the wifi?