INITIATION OF DEVELOPMENT IN EGG OF ARBACIA. 397 



eating that the butyric acid renders the egg more susceptible to 

 sea- water cytolysis (that is, the acid acts as a catalyst to the ordi- 

 nary cytolytic action of sea-water on the uninseminated egg), the 

 hypertonic sea-water of the concentrations used by the writer pos- 

 sesses three distinct actions : ( i ) It prepares the egg for cytolysis 

 as does butyric acid; (2) it cytolyzes as does the normal sea- water 

 following butyric-acid treatment; and (3) it corrects this cytolysis 

 as does the hypertonic sea-water as used by Loeb. Of course, this 

 may well be. It does seem, however, a rather cumbersome sug- 

 gestion. 



It would thus appear that the hypertonic sea-water being alone 

 sufficient, butyric acid is not necessary. Since, moreover, as I 

 have elsewhere pointed out (Just, '20), there are cogent reasons 

 for the position that butyric acid does not cause membrane separa- 

 tion through a superficial cytolysis, the superficial cytolysis-cor- 

 rective factor hypothesis becomes untenable. Rather it is far more 

 simple to explain the action of butyric acid and of the hypertonic 

 sea- water as used by Loeb as additive: together they accomplish 

 what the hypertonic sea-water alone in my experiments accom- 

 plishes. The butyric acid-hypertonic sea- water method, beautiful 

 though it is and technically brilliant, confuses the picture because 

 of the superficial cytolysis-corrective factor theory to which it 



gave rise. 



In any field the pioneer work is usually qualitative. The work 

 is none the less important therefor. And yet one can not but feel 

 that it is a pity that Loeb did not make exact observations with 

 various concentrations of salt particularly so since the method 

 involved is such a simple quantitative one. 



If, now, we reject the superficial cytolysis-corrective factor hy- 

 pothesis as an explanation of experimental parthenogenesis, what 

 explanation do we offer? While it seems to me, in the present 

 state of our knowledge of this subject, far more profitable to 

 collect data than to theorize, it is nevertheless true that the data 

 presented above permit at least a provisional hypothesis. Cer- 

 tainly, we may draw conclusions from the work if these be con- 

 sistent with the data. 



To begin with, it is difficult to conceive of the initiation of 

 development being fundamentally different for different ova. The 



