DIPLOID AND ANDROGENETIC HAPLOID HYBRIDIZATION BETWEEN TWO FORMS OF RANA PIPIENS, SCHREBER

1. Two distinct forms of frog, commonly referred to as Rana pipiens, Schreber, are described, and evidence is presented to show that they probably represent geographic races of that species, one from northern Vermont, the other from southeastern Pennsylvania.2. In the experiments described, the gametes of these two races have been combined reciprocally to form diploid and androgenetic haploid hybrids and the early development of these has been studied in detail.3. The diploid hybrids developed through metamorphosis; the androgenetic hybrids for 7 to 11 days, up to about stage 24 (Shumway, 1940).4. A comparison of 3-day-old control and hybrid embryos reveals that, in general, the combinations which include cytoplasm of the northern form are characterized by larger head primordia and smaller posterior axial structures than are observed in those with southern cytoplasm. Such dissimilarities, only slightly apparent between the homospermic diploid controls, become progressively more accentuated between the hom...