266 RALPH S. LILLIE. 



larval stages. The effect of such second treatment is in fact 

 indistinguishable from that of exposure to hypertonic sea-water 

 or cyanide. 



The problem of the nature of the effect produced on the egg by 

 hypertonic sea-water, or the other corrective agent employed 

 to supplement the membrane forming treatment, thus appears 

 in a simpler light. In the starfish egg, after membranes have 

 been formed as above, an exposure to {e. g.) 32° or to weak 

 butyric acid solution for several minutes constitutes a highly 

 favorable form of after-treatment, producing the same effect on 

 development as hypertonic sea-water or cyanide.^ This makes 

 it appear doubtful that two qualitatively distinct processes are 

 concerned in the activation of other eggs like the sea-urchin egg, 

 where some form of after-treatment, different from the mem- 

 brane-forming treatment, has hitherto proved necessary in order 

 to induce development in a high proportion of eggs. The condi- 

 tions are unlikely to be fundamentally different in the two 

 animals. In the starfish egg the "corrective" effect resulting 

 from after-treatment by heat has the same high temperature- 

 coefficient as the initial change underlying simple membrane- 

 formation by heat.^ This could hardly be the case if the two 

 processes were qualitatively dissimilar; it indicates clearly that 

 the same fundamental change in the egg-protoplasm furnishes 

 the conditions for both the membrane-forming process and the 

 "corrective" process. I have found that in the Arhacia egg 

 temporary warming (i to 6 minutes at 32°, 34° and 35°) does 

 not cause development (except in very few cases) even if followed 

 by hypertonic sea-water;^ and there is no evidence that pro- 

 longed treatment with weak fatty acid solutions will cause com- 

 plete development in this egg.^ The only highly and invariably 



1 Cf. the experiments summarized in Tables XIII to XVII below. 



2 Compare the experiments of Tables XIV and XV below. 



^ Unpublished experiments performed last summer. An occasional egg may 

 form a larva under this treatment, but the great majority remain unaltered. 



^ In the case of Strongylocentrotus purpuratus Loeb found that eggs exposed to 

 butyric acid solutions of the concentrations w/250, m/i66, and w/125 for more than 

 2 minutes failed to form membranes (" Artificial Parthenogenesis and Fertilization," 

 p. 141). Herbst found that eggs of Sphcer echinus treated for 2, 5, and 8 minutes 

 with a mixture of 50 c.c. sea-water plus 3 c.c. w/io acetic acid gave only occasional 

 larvae {Roux's Archiv, 1906, Vol. 22, p. 473). Apparently no systematic experi- 



