ACTIVATION OF UNFERTILIZED STARFISH EGGS. 267 



effective after-treatment hitherto discovered for the sea-urchin 

 egg is hypertonic sea-water.^ It would thus appear that the 

 conditions in this egg differ considerably from those in the 

 starfish; but the fact that a simple exposure to hypertonic sea- 

 water, if sufficiently prolonged, has the same effect in inducing 

 development as a briefer exposure to the same agent combined 

 with membrane-formation by fatty acid, seems to indicate that 

 the conditions are fundamentally similar in both types of egg, 

 and that a unitary process underlies activation in both cases. 

 The remarkable effectiveness of hypertonic sea-water with the 

 sea-urchin egg would seem to be due to certain special largely 

 incidental pecularities; temporary abstraction of water appears 

 for some reason to render this egg more resistant to the dissolu- 

 tion that otherwise results from the membrane-forming treat- 

 ment.2 In other eggs, however, like those of the starfish or 

 Nereis, hypertonic sea-water shows no special advantages over 

 a number of other forms of after-treatment. The fact that a 

 double form of treatment has hitherto proved especially effective 

 with the sea-urchin egg is thus not inconsistent with the view 

 that the activation-process is essentially unitary in character 

 in all eggs. 



Experimental. Effects of Simple Exposure to Warm 



Sea-water. 



In these experiments the procedure was similar to that de- 

 scribed in my earlier paper .^ Sea-water at a temperature slightly 

 above that chosen for the experiment was added rapidly to the 

 small beaker containing the eggs (with a thermometer) until the 



merits of this kind have yet been performed with Arbacia. At Naples, using 

 Arbacia pustulata, Lyon was able to cause development to larvae in ca. 10 per cent, 

 of eggs by exposure to sea-water acidulated with HCl, but he did not try fatty 

 acids {Amer. Journ. Physiol., 1903, Vol. 9, p. 310). 



1 Cyanide is only slightly effective with Arbacia punctulaia {cf. my experiments 

 described in Journal of Morphology, 1911, Vol. 22, page 703); it is more so with 

 Strongylocentrotus, according to Loeb's results (cf. "Artificial Parthenogenesis and 

 Fertilization," p. 80), but even here it is less uniformly favorable than hypertonic 

 sea-water. 



2 Cf. the experiments of Loeb (loc. cit.. Chapter XI; also Archiv fiir Entwick- 

 lungsmechanik, 1914, Vol. 38, p. 409). It is probable that hypertonic sea-water 

 has another and more distinctive mode of action (see below, p. 300). 



^Journal of Experimental Zoology, 1908, Vol. 5, p. 379. 



