Experimentally Produced Neoplasms in the Frog.

Abstract

It has been known that the frog egg on the stage of the second polar spindle-metaphase passes into a resting period, awaiting fertilization. Under natural conditions this lasts for only a few hours, but can be delayed up to 3 days without impairing perceptibly the vigor of the egg. After a further delay of 2 days, however, the eggs are dead. In the interval the eggs gradually lose their capacity to develop into normal embryos. The abnormality of these overripe eggs becomes manifest in the following features.1. The mechanism of control protecting normal eggs against polyspermy is impaired. As a consequence a high percentage of the overripe eggs show multiple segmentation. 2. In monosperm eggs the animal blastomeres are reduced in size, which effect seems to be due to a change in viscosity of the ovoplasm. 3. In the later development a marked tendency to produce axial duplications and supernumerary appendages is observed. These monstrosities as well as the polyspermy indicate a lack of control and coordinat...