THE PHYSIOLOGY OF FERTILIZATION 169 



with the above: ''The superposition of insemination 

 on the optimum hypertonic treatment does not in- 

 crease the percentage of development." This is in no 

 sense inconsistent with Loeb's statement that the block 

 to polyspermy is not due to changes necessarily con- 

 nected with development, whatever this may mean; 

 but it is a result that renders in the highest degree 

 improbable that reversal of activation of the egg occurs. 

 Activation is a part of the fertilization reactions, and 

 there remains no evidence that it is reversible, whether 

 induced by fertihzation or by artificial means. 



Godlewski (191 2) has shown that the sperm of 

 Chaetopterus will enter the eggs of sea urchins and cause 

 normal membrane formation; but such eggs do not 

 segment, and soon die. If, however, they are exposed 

 after the hybrid fertilization to the action of hypertonic 

 sea-water for a short period of time, they may segment 

 regularly and develop to larvae. He speaks of this as 

 superposition of parthenogenesis on hybrid fertilization. 

 This determination in no way runs counter to our inter- 

 pretation, however it may be named. It is quite clear 

 that the hypertonic sea-water has no activating effect 

 in this experiment, but on the contrary inhibits an in- 

 jurious effect of the foreign sperm. 



Herbst's experiments (1909 and 191 2), in which he 

 superimposed hybrid fertilization on partial partheno- 

 genetic activation and secured a shifting of inheritance 

 in the maternal direction, deal primarily with problems 

 of hybridization. As far as the problem of superposition 

 is concerned the experiments are perfectly consistent 

 with JVIoore's interpretation, because the parthenogenetic 

 activation was incomplete. 



