Bash passing a filename with a space into xargs?

How can I get this to recognize a filename with a space? 
I am manipulating files in my script, but at the portion where I want to do a diff. I cannot get it to work. 
Would someone out there know of a workaround?  (Besides saying "don't have filenames with spaces in them).  :-) 

This is in bash:
uno="try this.txt"
dos=blah.pdf
echo "$uno" "$dos" | xargs -l bash -c 'echo uno:$0 dos:$1' | xargs  	
#OUT: uno:try dos:this

echo "$uno" "$dos" | xargs -l bash -c 'echo uno:$0 dos:$1' 
#OUT: uno:try dos:this

echo uno:"$uno", dos:"$dos"  #this works, but doesn't help in my script.
#OUT: uno:try this.txt, dos:blah.pdf

thanks,
crzzy1