39 6 E. E. JUST. 



alone is sufficient for the production of plutei. So-called agents 

 of superficial cytolysis do, of course, improve results, but are not 

 absolutely essential. Moreover, for many eggs hypertonic sea- 

 water alone will initiate development; the majority of ova that 

 respond at all to agents that initiate development need but a single 

 agent. The egg of Arbacia is no exception. It is entirely unnec- 

 essary to use an agent of superficial cytolysis as either a primary 

 or secondary factor for the production of a high per cent, of plutei 

 of great degree of normality. 



Secondly, according to Loeb, the agent of superficial cytolysis 

 may be used either before or after the hypertonic sea-water. If 

 butyric acid is as effective after hypertonic sea-water treatment as 

 before, on what logical grounds can we speak of hypertonic sea- 

 water as a corrective factor for the superficial cytolysis yet to 

 take place? 



Finally, the hypothesis of a superficial cytolysis as part of the 

 theory of experimental parthenogenesis is untenable because it 

 assigns a role to hypertonic sea-water which is the opposite of that 

 of any agent of superficial cytolysis. Since, as shown above, the 

 hypertonic sea-water alone, if of sufficient strength, does just what 

 the butyric acid will do call forth membranes the case falls. 

 In order to save the theory, it would be necessary to assume that 

 the hypertonic sea- water of the strength used by the writer to 

 induce membranes has two effects. 1 First, it acts as butyric acid 

 by superficially cytolyzing the egg; and, second, it acts as a cor- 

 rective factor to correct its first effect. This interpretation in turn 

 entails assumptions which together make it worthy of no serious 

 consideration. 



If, for example, we insist that the first effect of hypertonic sea- 

 water is cytolytic, then we must change the connotation of the 

 word cytolysis. Further, the hypertonic sea-water employed by 

 the writer brings about membrane separation while the eggs are 

 in the solution. This fact, now, entails an interesting assumption: 

 since following butyric-acid treatment as employed by Loeb the 

 egg of Arbacia cytolyzes on return to sea-water, therefore indi- 



1 Loeb does make just this assumption. I must confess, though, that I 

 fail to follow his reasoning. See Loeb (" Artificial Parthenogenesis and 

 Fertilization." The University of Chicago Press, 1913, page 159.) 



