292 



E. E. JUST. 



which samples are removed at intervals and inseminated with 

 fresh sperm. Control eggs of bulk approximately equal to any 

 of the exposed lots are similarly inseminated. To save time and 

 material the eggs used for the study of cytolysis were frequently 

 used for this set of observations. Every precaution was exer- 

 cised to keep everything clean and sterile ; likewise to procure 

 conditions as uniform as possible. 



B. The Observations. 



The observations here presented are chosen for purposes of 

 comparison from those that have already been reported in the sec- 

 tion on cytolysis. And we may say at the outset that all these data 

 show that the duration of fertilization capacity of the under- and 

 the over-exposed eggs runs parallel with resistance to cytolysis. 

 Under-exposure, then, not only protects against cytolysis but 

 preserves the fertilization capacity ; while over-exposure which 

 hastens cytolysis likewise shortens the period after exposure dur- 

 ing which the eggs will fertilize their failure to fertilize con- 

 stitutes the best index of initial cytolysis. 



Experiment 2 B. June 14, 8:00 A.M. Eggs exposed to bu- 

 tyric acid for varying lengths of time then transferred to 250 

 c.c. of sea-water. Control in sea-water (see page 284). 



12:02 P.M. Samples from dishes Nos. I (control) and 2-12 

 inclusive inseminated with fresh sperm suspension. 



i : 50 P.M. Cleavages in these dishes of inseminated eggs 

 counted and percentages recorded as follows : 



Here eggs inseminated about four hours after exposure show 

 no cleavage in the over-exposed lots while the percentage of 

 cleavage in the under-exposed lots is high much higher in the 

 case of the ten second exposure than in the control. Eggs with 

 optimum treatment which form highest per cent, of membranes 

 show no cleavage. There is a difference, however, between these 



