Abstract
Sex chromosomes of the lizard, Cnemidophorus tigris (Baird and Girard), were analyzed in mitotic and meiotic cell divisions using C-band and G-band staining techniques. The X and Y are homologous along most of their lengths but do not crossover in the medial portion of the bivalent, where their centromeres lie. In this region the X and Y differ in centric position and heterochromatin. The similarities of the X and Y in C. tigris contrast to sex chromosomes in other animals, and probably represent an early stage of differentiation.