30 RALPH S. LILLIE 



In the experiments about to be described I have found that 

 anesthetics produce very definite effects of this kind with star- 

 fish eggs. UnfertiUzed mature eggs of Asterias forbesii treated 

 briefly with isotonic NaCl solution, dilute fatty acid solution, 

 or warm sea-water (35°), returned to sea- water for ten minutes, 

 and then exposed for half an hour to sea-water containing a 

 favorable anesthetic in appropriate concentration, yield a large 

 proportion — in some cases 80 to 90 per cent — of active larvae. 

 Such after-treatment is often more favorable than that with 

 hypertonic sea-water. With Arbacia eggs, on the other hand, 

 the results of similar experiments have been essentially nega- 

 tive. So far I have been unable to produce in these eggs any 

 marked increase in the proportion developing to a larval stage 

 by any method other than the use of hypertonic sea-water. Cya- 

 nide, in my experience, has proved only slightly effective. After- 

 treatment with sea-water containing an increased proportion of 

 magnesium and calcium salts (without altering the osmotic 

 pressure), or with sea-water containing anesthetics (as in the 

 solutions used below), is ineffective with Arbacia eggs. Just 

 why the two species should thus differ cannot definitely be said 

 at present; in general the starfish egg is the more responsive of 

 the two, and may be made to form membranes and develop by 

 various methods which have no effect on the Arbacia egg;-" it 

 is also more variable in its behavior and less resistant to inju- 

 rious influences. It is significant that the plasma membranes of 

 starfish eggs are much less resistant to the permeability-increasing 

 action of salt-solutions than are those of Arbacia eggs,^! and the 

 greater effectiveness of after-treatment with anesthetics may pos- 

 sibly indicate that the membranes undergo the reverse kind of 

 modification (permeability-decrease) also with greater readiness. 

 The difference in the degree of responsiveness would on this 

 view be an expression of differences in the properties of the plasma 

 membranes; these differences indicate differences of protoplasmic 

 composition, since the membrane is presumably a haptogen film 



2" Brief warming, shaking, isotonic NaCl solutions, weak solutions of mineral 

 acids, exposure to cold. 



21 Cf. my papers in the American Journal of Physiology, 1910, vol. 26, p. 125; 

 1911, vol. 27, p. 289. 



