INITIATION OF DEVELOPMENT IX CH/ETOPTERUS. 



47 



dency for adverse conditions to interfere first with cleavage, and 

 second to destroy the power of differentiation into swimmers 

 also (see Table X.). 



TABLE X. 



3. Excess of Oxygen in the Sea-water and Sperm. The effect of 

 an excess of oxygen in the sea-water is here considered as a 

 primary stimulus to artificial parthenogenesis and therefore 

 included with the other experiments of fertilization supple- 

 mentary to a physico-chemical parthenogenetic agent. When 

 sperm were added to eggs which had been for varying times in 

 oxygen-saturated sea-water, in one case the number of swimmers 

 resulting in the experiment was reduced one half or more from 

 that of the fertilized control. That the reduction was not due 

 to length of time after removing the eggs and sperm from the 

 animals was seen by making a fertilized control at each time 

 when an experimental lot was fertilized (Table XI.). 



TABLE XI. 



The sperm and eggs were evidently just as able to develop 

 normally at the end of the experiment as at the beginning. 

 Nevertheless the eggs which had been subjected to the action of 

 an excess of oxygen showed a much lower per cent, of swimmers 

 than the control, and the effect was great IT with longer time of 



