This paper deals with the evolutionary design of programs (constructors) that are able to create (n+2)-input circuits from n-input circuits. The growing circuits are composed of polymorphic gates considered as building blocks. Therefore, the growing circuit can specialize its functionality according to environment which is sensed through polymorphic gates. The work was performed using a simple circuit simulator. We evolved constructors that are able to create arbitrarily large polymorphic even/odd parity circuits and polymorphic sorting networks. Categories and Subject Descriptors B.6.1 [Logic Design]: Design Styles—Combinational logic; B.6.3 [Logic Design]: Design Aids—Automatic synthesis; I.2.m [Artificial Intelligence]: Miscellaneous General Terms Experimentation, Design Keywords Genetic algorithm, development, digital circuits design, polymorphic circuit