FERTILIZATION AFTER INITIATION OF DEVELOPMENT. 263 



to the latter solution is much more nearly an optimum treatment 

 for activation than is the weaker concentration. 



i . Fertilization after Exposure to Hypertonic Sea-water. 



The fundamental interest of the writer has been directed 

 towards the capacity of an egg, once activated by an artificial 

 stimulus, for fertilization. If an egg is fertilized normally, the 

 spermatozoon supplies the optimum stimulus for the initiation 

 of changes, latent within it, that lead to normal development. 

 But since these same changes may be initiated (it seems that 

 we must regard it so) by artificial agents, is there yet the possi- 

 bility of an observable stimulus from a spermatozoon if applied 

 subsequent to or during these changes? Can fertilization be 

 superimposed upon hyper tonic parthenogenesis? 



Eggs were exposed to the action of hypertonic sea-water as 

 given above, returned to normal sea-water and divided into 

 two lots, one of which remained standing at room temperature,, 

 while to the other was added a fresh sperm suspension. Let it 

 again be brought to mind that exceedingly variable results are 

 obtained from the same type of treatment of two different lots 

 of eggs and since the condition of the eggs before sperm are 

 added is the all-important factor for subsequent fertilization 

 one must be very careful to know as thoroughly as possible the 

 condition of the eggs in question. In one experiment one may 

 obtain only 3 per cent, of cleavages after a given hypertonic 

 treatment and at another time, under as nearly as possible 

 identical conditions, 25 per cent, to 35 per cent, cleavages. The 

 following experiment will indicate the method of procedure and 

 the results in general that have been obtained. 



From the results of this experiment one can readily see the 

 different capacities for fertilization possessed by eggs exposed 

 to the weaker solution (lot A) and those activated by the stronger 

 one (lot B). This relation can be seen at a glance from Fig. i, 

 the curves of which were plotted from this experiment. 



The lot of eggs returned to normal sea-water and inseminated, 

 after an exposure to the weaker solution A, for a period of ten 

 to twenty minutes, appear very little, if any, different from 

 the control lot of normally inseminated eggs, either as regards 



