282 E - E - J UST - 



" Ageing eggs cytolyze 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 con- 

 dition of the cytoplasm, a diminution in size of the protoplasmic 

 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 cyto- 

 plasm 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 normal. 



" 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 cytolysis 

 are seen at the same time. 



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

 other evidences of ageing, 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, cytolyzed 

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

 physiologic condition cytolyzed at a similar rate at the same tem- 

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



" In Toxopneustes, cytolysis in any considerable numbers was 

 first observed when ^5 hour old in experiment I, l /$ hour old in 

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

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

 rate of cytolysis is essentially the same as in Toxopneustes. 



" In Arbacia it was much slower. Beginning, in the given ex- 

 perimental conditions, in about 28 hours as in experiment 17, and 

 extending to 42 hours as in series 19, 46 hours in experiment 18, 

 .and later in other experiments. This difference in rate of cyto- 

 lysis is in part due to differences in temperature of the sea-water 

 in the two localities, but it is also due, and is another evidence of, 

 a protoplasmic difference in the two species of eggs." 



Now, the longevity of the egg in sea-water depends upon the 



