298 LOEB. 



beginning of the experiment, one of the flasks of each of the three 

 (. cultures was again opened. At this time nearly all the eggs of 

 the sterile culture were opaque or black, and a few were already 

 granular. In the two other cultures an equal percentage of the 

 eggs were opaque. The eggs, therefore, die just as rapidly in the 

 sterilized flasks which are absolutely free from bacteria as in the 

 flasks containing bacteria. Death follows from internal causes, 

 and so rapidly that the few bacteria in the sea water are scarcely 

 able to accelerate the death of the eggs. The eggs have already 

 died from internal causes before the bacteria can attack them in 

 sufficient numbers to threaten their existence. 



The flasks which were opened later served only to corroborate 

 what has been said. The experiment was repeated with the 

 same result. Each of the flasks that were opened during the first 

 few days also contained a small number of living transparent 

 eggs. The latter were, without exception, immature. The 

 experiment, therefore, shows that the mature eggs of starfish die 

 in the course of a few hours, and tliat the cause of this death 

 cannot be sought in flic bacteria of the sea water; and further, 

 that under c.ractlv the same conditions the immature eggs remain 

 alive. 



III. THE CHEMICAL CONDITIONS NECESSARY FOR MATURATION 



IN STARFISH EGGS. 



Since the eggs of Asterias are usually immature in the ovary, 

 but, in part, at least, maturate in the course of one or two hours 

 when introduced into sea water, the suspicion was aroused that 

 some of the substances contained in the sea water brought about 

 the maturation. In order to determine which substance this might 

 be, a series of solutions were prepared having approximately the 

 osmotic pressure of the sea water. The result was so simple that 

 i it is not necessary to describe all the experiments here. For it 

 was found that when the eggs are introduced into solutions which 

 contain free hydroxyl ions, maturation soqn follows, but that this 

 does not occur in solutions containing no hvdrpxyHons. So, for 

 example, the eggs retain their nucleus in a y&n NaCl solution, or 

 in XaCl solutions to which some potassium or calcium has been 

 added. If, however, .5 to 2 c.c. n/io NaOH is added to each 100 



