Copying and pasting between tmux panes containing vim instances over SSH in Terminal.app

I use vim to develop Perl code on a remote Linux box running Debian Jesse. The machine is a virtual machine running in VirtualBox. I use ssh and then issue a vim command to start editing the file. I've been experimenting with tmux on the remote machine to see how I like it. But I cannot for the life of me figure out how to copy and paste text between vim instances in two different tmux panes. I'd prefer to be able to use both the mouse and vim-like keystrokes (yy, dd p) to do this. I've tried just about every recommendation out there for trying to get this to work but I haven't gotten anywhere. I'm running El Capitan. Is there a definitive answer out there for getting this to work?