254 ARTHUR RUSSELL MOORE. 



Herlant apparently assumes that the action of the hypertonic 

 solution must be subsequent to the acid treatment, that to be 

 effective such action must occur in a certain phase of the rhyth- 

 mical activity of the centrosome. Since in Strongylocentrotus 

 purpuratus treatment of the eggs with the hypertonic solution 

 may precede that with acid sea water by as much as a forty-eight 

 hour interval with the result that normal parthenogenetic larvae 

 are formed,^ Herlant's contention is not justified. Furthermore, 

 treatment of the eggs with small quantities of KCN or depriving 

 them of oxygen, may replace hypertonic treatment after fatty 

 acid. Now lack of oxygen or the repression of oxidations does 

 not cause aster formation, but on the contrary suppresses it. 

 In fact it has even been shown that in Arbacia the first steps in 

 development induced by the acid treatment may be reversed 

 and the egg returned to its resting stage with its original possi- 

 bilities of fertilization, simply by withholding oxygen from such 

 an egg or by treating it with KCN.^ In view of these facts, 

 it seems evident that Herlant's conclusion that the hypertonic 

 solution is a necessary factor in artificial parthenogenesis because 

 it controls aster formation, does not hold. 



As to the rhythmicity in effectiveness of the hypertonic treat- 

 ment which Herlant found in his experiments, it seemed possible 

 that the relation between the time spent in normal sea water 

 after acid treatment and the time in the hypertonic solution 

 might have a bearing upon the question. Six years ago the 

 present writer found, in working with the eggs of Strongylocen- 

 trotus purpuratus , that if the exposure to normal sea water in 

 such an experiment be lengthened, the subsequent treatment 

 by hypertonic sea water must be shortened to secure optimum 

 results.^ Repetitions of the experiment at Woods Hole during 

 the past summer, however, have indicated that the relation does 

 not exist for Arbacia. 



Table I. shows the results of dividing a lot of Arbacia eggs, 

 after fatty acid treatment, into three parts which remained in 

 normal sea water, 5, 25 and 90 minutes respectively, before 

 being put into hypertonic sea water. In each case a portion 



1 J. Loeb, Journ. Exp. Zool., vol. 15, p. 201. 



2 J. Loeb, Science, N. S.-, Vol. 38, p. 749. 



8 J. Loeb, "Artificial Parthenogenesis and Fertilization," p. 96. 



