784 SALT ANTAGONISM IN STARFISH EGGS 



The jelly is readily and rapidly removed from the eggs by washing 

 in pure isotonic NaCl solution (0.54 m). This is most conveniently 

 demonstrated as follows. Sea water containing a suspension of the 

 eggs is gently centrifuged with a hand centrifuge, with ten or twelve 

 slow turns, so as to collect the eggs in the narrow end of the tube; 

 the sea water is poured off and replaced by pure 0.54 m NaCl; the 

 tube is then inverted to suspend the eggs and again slowly centri- 

 fuged as before; the solution is poured off and replaced with fresh, 

 and this process is repeated. The eggs are thus exposed to the pure 

 NaCl solution free from all but traces of sea water. If they are then 

 returned to sea water and examined in India ink, the jelly is found 

 to have completely disappeared. There is no evidence of further 

 secretion of jelly by eggs which have thus been freed from it and re- 

 turned to sea water. 



Removal of the jelly leaves the power of fertilization and devel- 

 opment unimpaired. Thus, in a typical experiment unfertilized eggs, 

 removed from the animal 45 minutes previously, were exposed for 

 6 minutes to 0.54 m NaCl with two changes of the solution and cen- 

 trifuging as above. Examination in India ink showed complete 

 removal of the jelly from all eggs. Sperm was added to part of the 

 eggs 18 minutes after the return to sea water. A majority next 

 day had formed blastulae; abnormalities were, however, more frequent 

 than in the untreated control eggs and about 20 per cent had died 

 without development; this injurious effect is to be referred to the 

 action of the pure unbalanced solution upon the eggs. Similarly, 

 eggs freed from jelly subsequently to fertilization continued de- 

 velopment and formed blastute, although showing also a larger 

 proportion of abnormalities than the control. 



Arbacia eggs treated as above with 0.54 m NaCl show a similar 

 disappearance of the jelly, but the same effect is seen in sea water 

 and in solutions of NaCl containing CaCl2. In this species the jelly 

 is more soluble than in Asterias and the difference between pure 

 and calcium-containing NaCl solutions is not shown by the above 

 method. This difference in the properties of the jelly layer in the 

 two species indicates a specific difference of chemical composition, 

 but so far I have made no attempt to investigate this difference in 

 detail. 



