ANDROGENETIC DEVELOPMENT OF THE EGG OF RANA PIPIENS

Abstract

1. A technique is described by which the second maturation spindle and so all of the maternal chromatin can be removed from the egg of R. pipiens following its activation and penetration by the sperm.2. The operation as applied to this egg is considered satisfactory for a large number can be treated in a short time, the maturation spindle is removed with certainty, and the slight amount of cytoplasm removed has no destructive effect on the development which follows.3. Between 90 per cent and 100 per cent (generally 100 per cent) of the operated eggs undergo first cleavage simultaneously with the controls, and of these the majority develop for eight days, a few considerably longer.4. The development of androgenetic haploids compared with diploid controls of the same age m abnormal and delayed. Certain features of external and internal morphogenesis are described.5. It is shown that 90 per cent of the operated eggs can be expected to develop as haploids. This haploid nuclear condition remains unchanged until the final stages of development and then is altered only by the presence of a very few diploid nuclei.6. As is typical for haploids, the cells and nuclei of these androgenetic embryos tend to be smaller than those of the diploid controls.7. The development shows a high degree of uniformity from animal to animal over the first five days after which the differences become more pronounced.8. Yolk disappearance from the cells of the haploids is notably delayed.9. The ease of production and the success of development of R. pipiens androgenetic embryos seems to provide one of the best possibilities so far encountered for the study of haploid morphogenesis from eggs which normally develop as diploids.