EFFECTS OF AGING UPON GERM CELLS. IJ 



when fertilized. In either event the end result seems to be 

 essentially the same as in the sea-urchin eggs, namely fewer 

 develop, more become irregular or abnormal, with the age of the 

 mother. 1 The early history of the changes in the sea-urchin 

 egg and sperm as they deteriorate, we now know, and it is very 

 probable that the eggs of aging mothers undergo fundamentally 

 similar changes. 



The experiments with aging eggs throw light upon, and 

 indicate the probable cause of seemingly conflicting results in 

 hybridization experiments. 



The Hertwigs ('86) affirmed in contradistinction to the con- 

 clusions of Pfluger ('82) and Born ('83) that hybridization took 

 place the more readily when the eggs were of lower vitality. 

 Vernon ('98) also noted that the chances of hybridization were 

 increased when the eggs had previously been kept for about nine 

 hours in sea water, which, I have shown, lowers the vitality of the 

 eggs. Hagedorn ('09) discovered another method for increasing 

 the chances of hybridization, namely by increasing the HO 

 concentration of the sea water. Herbst, Tennent, Godlewsky- 

 Loeb and Kupelweiser used various modifications of Hagedoorn's 

 method and obtained similar results. But as will be later shown, 

 the increased alkalinity of the sea water only served to increase 

 the rate of deterioration of the eggs, and hence prematurely 

 aged them; these eggs showed the same changes which I have 

 described in aging eggs, changes which permit the ready entrance 

 of multiple autogenous sperm, or heterogenous sperm, and hence 

 give rise to abnormal development or to hybridization. 



Similarly, Doncaster, Vernon, and Herbst observed that hy- 

 bridization could be increased by raising the temperature of the 

 sea water. This also I have shown serves merely to preco- 

 ciously age the eggs and hence makes greater hybridization 

 possible. 



Less effective was the use of dilute sea water used by Ten- 

 nent and Herbst. Here again, dilute sea water increased ioni- 

 zation, and hence increased the metabolism of the egg, w^hich in 

 turn increased the rate of aging. 



1 The age of the sperm or the father is far less important than the age of the egg 

 or of the mother. 



