EXPERIMENTS ON THE NORMAL MEIOTIC BLOCK IN THE OVUM OF TRITURUS VIRIDESCENS

¹ Department of Biology, Emory University, Atlanta 22, Georgia

1. The oviducts of the newt, Triturus viridescens, were ligated at several levels to retain oocytes from 48 to 72 hours in the coelom or in certain regions of the oviducts. Eggs were collected and studied to determine the stage of meiosis, with the finding that advances past metaphase II, the normal stage of arrest, occurred at a low frequency, but were confined to eggs never exposed to the jelly secreted by the oviducts.

2. Twenty-two per cent of the eggs removed from the coelom or ostium of the oviduct and kept in vitro advanced past metaphase II, but eggs with jelly coverings did not advance. One doubtful advance was observed in an egg from which the jelly had been removed prior to its stay in vitro. Some "advanced" eggs exhibited post-meiotic "mitotic" activity.

3. The general problem of meiotic blockage in the egg is discussed. The jelly secreted by the oviducts is of significance with regard to meiotic arrest under the conditions of the experiments reported, and may play some role in normal arrest. The evidence does not, however, allow a decision as to the source of meiotic inhibition.