DEATH AND PROLONGATION OF LIFE IN THE EGG 207 



that the corrective effect if once imparted is permanent. If the 

 corrective factor alone were the life-saving factor, eggs treated 

 with a hypertonic solution alone should live indefinitely, or at 

 least much longer than the non- treated unfertilized eggs. This 

 is, however, not the case. In all the experiments the unfertilized 

 eggs of purpuratus treated with the hypertonic solution alone 

 died as quickly as those not treated at all, that is, in three days 

 or less, at room temperature. For these eggs the artificial mem- 

 brane formation became a life-saving act; while the artificial mem- 

 brane formation had just the opposite effect in sea urchin eggs, to 

 which the corrective effect was not imparted. This admits of 

 only one conclusion, namely that the life-saving effect of the 

 act of fertilization is not due to one but to the combined action 

 of both factors of fertilization. 



This harmonizes with the observations on the eggs of such 

 forms as the starfish (Asterina) in which the artificial membrane 

 formation by a fatty acid suffices to call forth development. Not 

 all the eggs, however, will develop into larvae under the influence 

 of artificial membrane formation alone, but only a small percent- 

 age. R. S. Lillie has shown that the percentage of eggs of Asterias, 

 which will develop into larvae after artificial membrane forma- 

 tion by heating, can be increased by a subsequent suppression of 

 oxidations in such eggs (which treatment as the writer has shown 

 can also supply the second factor of fertilization). This proves 

 that in the egg of the starfish fertilization is also induced by two 

 factors, but that some of the eggs possess or can produce the 

 second factor normally, while this factor can be produced in the 

 majority of eggs only if they are kept without oxidations for 

 some time. In the sea urchin eggs it is a rare exception if the 

 egg contains the second factor normally, that is, if it can develop 

 into a larva by the mere act of membrane formation. As a rule, 

 the second factor has to be supplied either by a treatment with 

 a hypertonic solution or by a prolonged suppression of oxidations. 

 The mature eggs of the starfish die without exception if they 

 are not fertilized and they die much more rapidly than the un- 

 fertilized eggs of the sea urchin; while the mere artificial mem- 

 brane formation saves at least the life of a small percentage of 



