428 E. I. WERBER 



Bataillon (I.e.) has observed a very marked tendency to 

 fragmentation and formation of double embryos in eggs of 

 Petromyzon which had been retained in the females for several 

 days after stripping. Since no modification of the environment 

 whatsoever was employed in this case, Bataillon speaks of 'blas- 

 totomie spontaneV as the factor responsible for duplication. 



Of the causes underlying this apparent deterioration of 'stale 

 eggs' Goldfarb ('16, '17 a and b) has made a systematic study. 

 He finds that it is apparently due to a progressive increase in 

 their permeability and to the thus resulting rise in the rate of 

 their oxidation, as postulated long ago by J. Loeb. 



I am inclined to attribute considerable importance to this 

 factor in our experiments in which, usually, eggs of several 

 females were fertilized together before they were subjected to 

 the action of the environmental modification. In other words, 

 the material of our experiments was of a varying viability and 

 varying susceptibility, the 'younger' eggs being less susceptible 

 than the 'older' ones. This variability cannot well be obviated 

 in any experiments of an explorative nature. For a single 

 female of Fundulus heteroclitus will not yield eggs enough for 

 a coherent series of experiments in which the same environ- 

 mental modification is employed, but differing in each experi- 

 ment in degree or in the stage at which the eggs were subjected 

 to it. Besides, it is well known that not all eggs spawned by, 

 or stripped from, a female at the same time are of the same 

 'maturation age.' It is a common experience to find mature 

 and immature eggs in the same female during the spawning 

 season, a fact which well indicates that the mature eggs have not 

 all matured at the same time. 



To this variation in degree of susceptibility of the eggs may 

 be due the enormous range in variation in the end-products of 

 development — from apparently perfectly normal embryos to 

 monstrosities of a most bewildering kind. The duplicities which 

 were recorded in our experiments are an incident in this almost 

 endless 'series.' They result primarily from duplication of the 

 embryonic primordium by blastolysis. And they as well as 

 all other monstrosities are expressions of the variation in the 



