FERTILIZATION-REACTION IN ECHINARACHNIUS PARMA. 293 



eggs with membranes and the over-exposed eggs; for, as pre- 

 viously shown (Just, 'ipO, e gg s with membranes the instant of 

 membrane elevation are incapable of fertilization ; on the other 

 hand, the over-exposed egg is fertilized on removal to sea- 

 water. Its capacity for fertilization endures for one hour or 

 more. 



Experiment 6 B. June 16, 1 : 30 P.M. Eggs of Experiment 

 6 B whose percentages of cytolysis noted at 8:00 A.M. (see 

 page 285) inseminated at 1:30 P.M. Cleavage counts at 4:30 

 P.M. follow: 



Eggs we note that received a I5~second exposure show twenty- 

 two and one half hours afterward 75 per cent, cleavages whereas 

 normal eggs which have been in normal sea-water for the same 

 length of time have lost completely their capacity for fertilization. 

 This is by no means a solitary rinding; the acid treatment mark- 

 edly benefits the egg in protecting it against loss of fertilizing 

 power. Activated eggs and over-exposed eggs have lost their 

 capacity for fertilization. 



Experiment 8 B. June 17, 8:35 A.M. 13 hours after ex- 

 posure to butyric acid for o, 15, 20, 25, 30, 35, 40, 50, 60, 120 sec- 

 onds, eggs inseminated with fresh sperm suspension. 



12:00 M. No cleavage in any dish. 



These eggs lost their fertilization capacity relatively early. 



Experiment 13 B. June 25, 5:50 P.M. Eggs from each of 

 the dishes of the series exposed at 1 1 : 20 together with control 

 (No. i) inseminated with fresh sperm suspension. 



7 : 30 P.M. Good cleavages with membranes up to and in- 

 cluding No. 5. Best cleavages as to per cent., form, and size in 

 Nos. 2, 3, and 4. Dishes set aside overnight. 



June 26, 8 : 30 A.M. " Swimmers " counted in dishes, per 

 cent, noted as follows : 



