CHROMOSOME COMPLEMENT: DIFFERENCES BETWEEN EQUUS CABALLUS AND EQUUS PRZEWALSKII, POLIAKOFF.

The chromosome number of the domestic horse is 2n = 64; different races have the same complement. The chromosomes of two Przewalski's horses (at Catskill Game Farm, New York), presumably ancestral wild horses from Mongolia, are identical: 2n = 66, with more acrocentric and fewer metacentric elements than the chromosomes of the domestic horse. This apparent difference in karyotype may help resolve the questions of "purity" in the relatively few remaining Przewalski's horses. Moreover, these findings are of interest in relation to the apparent fertility of hybrids between these species.