284 RALPH S. LILLIE. 



an inverse relation exists between the concentration of fatty acid 

 and the time of exposure required to produce a given effect. 

 Systematic experiments to determine the character of this rela- 

 tion have not yet been carried out, but there are some observa- 

 tions bearing on this question. In several of my experiments in 

 the summer of 1912 starfish eggs exposed for only one minute to 

 acetic or butyric acid of ca. w/176 concentration (6 c.c. w/io 

 acid plus 100 c.c. sea-water) formed a large proportion of larvae.^ 

 Lyon observed some years ago that the exposure required to 

 induce parthenogenesis in Arbacia pustulata by means of weak 

 solutions of HCl in sea-water decreased with increase in the con- 

 centration of acid up to a certain point. ^ The minimum exposure 

 to n/260 butyric acid required to form membranes is very brief 

 in starfish eggs. Experiments last summer showed that while 

 10 seconds was insufficient to form membranes in more than a 

 few eggs (ca. 10 per cent.), with 20 seconds all formed membranes, 

 followed by the typical irregular changes of form and breakdown. 

 After one minute's exposure to w/260 butyric acid an occasional 

 egg may form a blastula; yet in the series showing the shortest 

 optimum exposure of any performed last summer (No. 5, Sept. 2) 

 at least 3 minutes was required to enable any considerable 

 proportion of eggs to develop to a larval stage. The parallelism 

 between the effects of high temperature and of weak fatty acid 

 solutions indicates that the two agents act by producing the same 

 kind of change in the egg-system. More detailed experiments 

 to determine the influence of concentration as well as time on the 

 action of this and other cytolytic substances remain to be carried 

 out, and their results will probably throw further light on the 

 nature of this change. 



Effects of Membrane-formation by Heat or Fatty Acid 

 Combined with After-treatment by the Same Agent. 



The fact that a longer treatment with the membrane-forming 

 agent produces the same effect as a short treatment combined 

 with after-exposure to hypertonic sea-water or cyanide suggests 

 that a suitable after-treatment with the membrane-forming 



1 Cf. Journal of Experimental Zoology, 1913, Vol. 15, pp. 41, 42. 



2 Lyon, Aiy.erican Journal of Physiology, 1903, Vol. 9, p. 310. 



