>There is probably a simpler solution, but my design calls for a shell
>variable (say a) which has an integer value to be used to reference
>another "shell variable", specifically the contents of a specified
>argument ... so, if I have set a=5, I would expect that I could do an
>echo "The fifth parameter is $a" and have it printed ... but instead I
>get "The fifth parameter is 5" .... have tried most every combination of
>"" and ' ' (as well as ` `) to no avail ... any suggestions?

Doesn't work.  You can't do any kind of double indirection in the 
shell.  This is an inconvenience, but part of life.