UNFERTILIZED STARFISH EGGS. 303 



glass tube described above, in which the deeper layers suffered 

 from lack of oxygen. A second portion was introduced into a 

 small flask through which a steady stream of pure oxygen was 

 passed. On the following morning, that is to say, fifteen hours 

 after the eggs were brought into the atmosphere of pure oxygen, 

 the various portions of the eggs were examined. The eggs intro- 

 duced into the current of oxygen showed in one vessel 9$ per 

 cent, mature and dark, dead eggs and 2 per cent, immature 

 Ik'in? eees. The esfs^s which had remained in normal sea water 



ijS C^ & C> O 



contained, as before, about 75 per cent, mature eggs, all of which, 

 however, were black and dead, with the exception of a few eggs 

 which had begun to divide, 1 and were living. 



The immature eggs were also still living. Upon the other hand, 

 the eggs which had been left in the glass tube in absolute or tl 

 relatively high lack of oxygen, were nearly all living ! This 

 observation seems to show that the same processes which lead to 

 the maturation of the egg bring about its death if they are not 

 inhibited at the right time. In this way the process of fertilization 

 becomes a life-saving or life-prolonging act. 



Y. Do THESE FACTS HOLD FOR OTHER FORMS? 



The question of the relation between maturation and natural 

 death can be studied most beautifully in the starfish egg because 

 it is possible to obtain it in an immature condition, and because 

 maturation follows very rapidly. With sea-urchin eggs conditions 

 are much less favorable, since the egg maturates within the 

 ovary, and since it is difficult to obtain immature eggs during the 

 spawning season. I have, therefore, been unable to discover which 

 chemical factors determine the maturation of the sea-urchin egg, 

 and to decide whether the same circumstances cause the death of 

 the sea-urchin egg that bring about the death of the starfish egg; 

 and whether the life of the sea-urchin egg can be prolonged 

 through a prevention of these circumstances. In an indirect way 

 Lewis and I attempted to answer this question last year, when we 

 assumed that the destructive processes which bring about the 



1 This cleavage was possibly brought about through mechanical agitation ; 

 I had repeatedly shaken the dish to facilitate the introduction of oxygen into 

 the sea water. 



