EFFECTS OF AGING UPON GERM CELLS. 9 



CYTOLYSIS OF AGEING EGGS. 



The consummation of the various deteriorating changes in 

 aging eggs is cytolysis and death. 



Cytolysis of sea-urchin eggs under the influence of various 

 experimental conditions, such as saponin, salycyl aldehydes, 

 propyl alcohol, distilled water, etc., have been carefully described 

 by Loeb. Loeb speaks of two methods of cytolysis, which he 

 calls "white "and "black." 



Aging eggs cytolize in the same two ways. In the "white" 

 or cytolysis by liquefaction, a changed permeability of the cortical 

 layer permits an increasing volume of sea water to enter the egg 

 with a corresponding enlargement of the egg, a more viscous 

 condition of the cytoplasm, a diminution in size of the proto- 

 plasmic granules, and an increasingly hyaline and translucent 

 appearance of the egg. In the second type of cytolysis, there is 

 either far less increase in size of the egg or no increase at all; 

 the central mass remains opaque and becomes increasingly 

 opaque; the cytoplasm is far less viscous; the outer surface which 

 is hyaline is fragmented, and sometimes the inner mass as well, 

 ' is fragmented, and the outer fragments fall off, with a consequent 

 diminution in size of the eggs, even far below the norm. 



I was unable satisfactorily to establish whether these two are 

 independent methods of cytolysis, possibly associated with 

 different degrees of virility of the eggs or whether they are 

 sequential phenomena. In most cultures, both types of cy- 

 tolysis are seen at the same time. 



The onset differs in the eggs of different females, and, as in 

 other evidences of aging, this variation is due to differences in 

 the physiologic condition of the eggs at liberation. Those eggs 

 which were in good physiologic condition at liberation, cytolized 

 late; those in poor condition, early. Eggs in relatively similar 

 physiologic condition cytolized at a similar rate at the same 

 temperature. The greater the temperature, the greater the rate. 



In Toxopneustes , cytolysis in any considerable numbers, was 

 first observed when - hour old in experiment I, -5- hour old in 

 experiment 3, 6 hours old in experiment 2 and 5, II hours old in 

 experiment 4, 20 hours old in experiment 9. In Hipponoe, the 

 rate of cytolysis is essentially the same as in Toxopneustes. 



