232 E. G. SPAULDING. 



The character of this rather remarkable curve is obvious. Up 

 to within twelve minutes after fertilization the resistance remains 

 the same, but from this point on it gradually rises up to either 

 just before or the beginning of the first cleavage ; during the earl}' 

 part of cleavage it falls to zero, with a sharp rise afterwards and 

 a fall at the second segmentation. 



The more important question however is to get at its meaning. 

 To get at this we take, corresponding to the general rise in im- 

 munity up to the time that cleavage is beginning, the greater 

 demand for oxygen, established by Lyon in his work this summer. 

 This might mean in view of the fact that either at least just pre- 

 ceding or for sonic time before cleavage an increase in osmotic 

 pressure must take place, as we have shown, either one of two 

 things to account for this, viz., either that the oxidation process 

 is at first synthetic and subsequently determines analytic events ; 

 or that it is analytic from the start. Also to be correlated with 

 this is the known effect of ether as a better solvent than is water. 

 This is identical with its causing a greater degree of solution and 

 consequently an increased osmotic pressure. The inhibiting 

 effect of the ether on the eggs at the critical period in the above 

 curve may be ascribed then, we believe, to its augmentation of 

 the normal predominence in osmotic pressure at that time, i. e., 

 to its increase of that difference of potential in the direction of 

 pressure-tension necessary for cleavage. Accordingly in the 

 equalization of this augmented potential difference the eggs would 

 be expected to increase in size more than usual in their attempt 

 to divide, and this is confirmed by the observed sivollen appear- 

 ance, even when as in some cases division takes place once and 

 then stops. 



This increasing immunity up to the maximum can be explained 

 then in two possible ways. If synthetic as simple oxidation proc- 

 esses precede the analytic then during that period there is some- 

 thing to oppose the dissolving effect of the ether ; but since this 

 opposition would seem to exist equally all through the precleavage 

 period, the rise in immunity would be hard to account for in this 

 way. On the other hand if analytic processes take place from 

 the start as a result of the use of oxygen then the longer before 

 cleavage that the exposure to ether is made the greater should be 



