MATURATION, NATURAL DEATH AXD THE PRO- 

 LONGATION OF THE LIFE OF UNFERTILIZED 

 STARFISH EGGS (ASTERIAS FORBESII) AND 

 THEIR SIGNIFICANCE FOR THE THEORY OF 

 FERTILIZATION. 



JACQUES LOEB, 



HULL PHYSIOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



I. INTRODUCTION. 



I have pointed out in my earlier publications that fertilization 

 of the egg serves to prolong the life of the egg. 1 



The mature unfertilized egg dies in a comparatively short time. 

 Because of this fact the egg becomes of importance as an object 

 of experiment, to study the question of natural death and pro- 

 longation of life. For by no means has it been decided that there 

 is a '' natural " death. We only know that with an increase in 

 age a critical period is reached in which every living organism dies 

 under the influence of conditions which do not affect a younger 

 organism. It may, therefore, be of interest that we are able to 

 show, as I believe, that a critical_rjeriod exists in the life of many 

 eggs in which they die a " natural " death, and that the life of the 

 eggs can, during this period, be saved or lengthened only through 

 various external conditions. 



The esfs: of the starfish (Astcrias Forbcsii) serves as a verv 



o o * 



favorable object of experiment in the study of this question. 

 \Yhen removed from the ovary this egg is generally " immature," 

 but as soon as it comes in contact with sea water it begins to 

 : ' maturate/' 



Morphologically, the immature state is characterized by a very 

 large, plainly visible nucleus. 2 The process of maturation consists 



1 Loeb, J., American Journal of Physiology, Vol. IV., 1901; Loeb and 

 Lewis, ibid., Vol. VI., 1902. 



2 The recent beautiful experiments of Delage have shown that, beside these 

 visible changes in the nucleus, chemical, but morphologically invisible, changes 



r 



also occur in the protoplasm. Delage, Etudes experimentales sur la matura- 



^ 



lion cytoplasmique et sur la parthenogenese artificielle chez les Echinodermes, 

 Arch, dc Zoologic experiment., Vol. IX., 1901. 



