NOTE CONCERNING THE ORIGIN OF POLARITY IN 

 THE FROG'S EGG. A CORRECTION. 



A. W. BELLAMY. 



In connection with work published in 1919 (BiOL. BULL., Vol. 

 37: 312-361) on the modification and control of development in 

 the frog egg, it seemed desirable to determine if possible the ori- 

 gin of the polarity of the egg. The position taken was that po- 

 larity must be either a matter of inheritance or of determination 

 by factors external to the egg. If the former possibility is true 

 the problem is, of course, simply made more remote. The second 

 possibility, since it is known or believed that polarity arises in a 

 number of plant and animal eggs, in response to external factors, 

 seemed the logical One to test, especially since it is the one most 

 readily investigated experimentally. The first question was to 

 determine the relation, if any, between the polarity of the egg and 

 its mode of attachment to the ovarian membrane. Here it was 

 found and it has since been confirmed, that in 75~8o per cent, of 

 the cases, the pedicle which attaches the follicle to the ovarian 

 membrane, is located on or within 20 of the equatorial region of 

 the egg. Since a band 40 wide over the equatorial region of a 

 sphere involves only about 34 per cent, of the total area it would 

 seem that the pedicle is not located at random over the surface 

 of the egg but with reference to some other factor, or factors. 



Since the polar axes of the ovarian eggs bear every relation to 

 gravity this factor is made highly improbable as having any in- 

 fluence on the origin of polarity. 



The next question to arise was the relation of the polarity of 

 the egg to its food and oxygen supply the blood flowing through 

 the follicular vessels. From observations made at that time on 

 both injected and living specimens I believed and stated, p. 321, 

 of the above mentioned paper, that ' ... in every case observed, 

 the greater part of the arterial blood supply was restricted to the 

 pigment hemisphere " and that the blood supply of the unpig- 

 mented hemisphere was largely venous. It was further sug- 



