EFFECTS OF AGING UPON GERM CELLS. 15 



all the eggs of a given female are in the same or nearly the same 

 physiologic condition, when freshly liberated, is misleading and 

 frequently very inaccurate. 



It has been held by Minot that senescence of the individual 

 began, not after sexual maturity, but far back in the history of the 

 individual, even before birth. My studies on aging eggs lead me 

 to the conclusion that senescence of the individual may be 

 traced as far back in the history of the individual as the matura- 

 tion of the egg. The aging eggs show numerous evidences of 

 senescence, not only during the egg stage but throughout their 

 development including their larval stage. And it is very prob- 

 able indeed that the effects are carried into the adult stage of the 

 individual. 



The value of the results depends upon the acceptance of the 

 technique used. The freshly liberated eggs were placed under 

 conditions that preliminary tests had shown were optimum for 

 that particular species of sea-urchin egg, namely: (i) the sea 

 water used had been collected at the height of the incoming tide, 

 and so obtained a more constant grade of sea water, and more 

 free of detritus, etc., (2) the sea water was filtered (with certain 

 precautions) and stored in glass ; (3) standard flat bottom bowls 

 were used, in which the concentration of eggs was far below 

 the injurious limit, and nearly constant for the different series; 

 (4) the volume of sea water was large enough to prevent inter- 

 ference by evaporation, etc. (250 c.c.) ; (5) the supernatant sea 

 water as well as the bowls were changed at least once a day; 

 (6) the temperature was kept fairly constant and close to that of 

 sea water in the open, etc. 



Under these conditions the freshly liberated eggs (whatever 

 their physiologic condition may have been at the time of libera- 

 tion) underwent a graded series of morphologic and physiologic 

 changes, which were not new processes or changes, but the 

 continuation of the same changes which took place within the 

 body before liberation, namely, loss of jelly, retardation of 

 membrane formation, increase in size of the egg, decreased rate 

 of division and decreased ability to cleave, etc. 1 



The rate of change was however accelerated. Such accelera- 



1 And it is very probable indeed, that these changes occur in a state of nature. 



