Abstract. We show that there are many natural algebraic constructions under which dualisability is not always preserved. In particular, we exhibit two dualisable unary algebras whose product is not dualisable.

AMS Subject Classification (1991): 08A60, 08C15, 18A40

Keyword(s): Natural duality, dualisability, unary algebra

Received December 8, 2000, and in final form March 16, 2001. (Registered under 2857/2009.)