How to do ........................................ this ?

I would like to format paragraphs such that the last word (or sometimes more than one word) is right justified, with the space before it filled with a series of dots,

similar to the table of contents in the Adobe Framemaker 7.0 manual (except they have numbers on the right).  I want to use this to define biological dicotomous identification keys.  The lines would look something like this:

1.  This is a line of text .......................................................... Homo sapiens

1'.  Another line of text ........................................................... Homo erectus

Any ideas?  Thanks in advance!