question regarding macros

[dxs@evolving.com (Dan Stanger)]

i have defined a macro as follows.
(defmacro schema (n d p)
  (let ((cd (compile-definition-part d)) (cp (compile-predicate-part p)))
  `(defclass ,n () ,cd)
(break)

...
when the break occurs  n has the value x.  if i then try to execute
(make-instance 'x) i get the error message x does not name a class.
could somebody explain this problem to me.
thanks,
dan stanger