FERTILIZATION REACTION IN ECHINARACHNIUS PARMA. 



13 



II. 



It has been shown (Just, '19) that the fertilization of eggs of 

 Echinarachnius by Arbacia sperm is greatly facilitated by the use 

 of alkali or by heavy insemination. Though giving a lower per 

 cent, of cleavage than alkali, heavy insemination was for several 

 reasons the method adopted in the experiments made to determine 

 the effect of Echinarachnius blood on fertilization by Arbacia 

 sperm. That this cross is inhibited by blood was suggested in the 

 earlier work. The experiments now cited indicate that this is 

 true. I cite four experiments made in June and in August, 1920. 



Uninseminated eggs of Echinarachnius are washed in sea-water 

 and allowed to settle. Five drops of this suspension is distributed 

 equally among five dishes as follows : Lot A, uninseminated in 

 sea-water ; Lot B, inseminated in sea-water with Echinarachnius 

 sperm; Lot C, inseminated in 3 per cent. Echinarachnius blood 

 with Echinarachnius sperm; Lot D, heavily inseminated in 3 per 

 cent. Echinarachnius blood with shed Arbacia sperm ; Lot E, heav- 

 ily inseminated in sea-water with shed Arbacia sperm. The re- 

 sults follow: 



In some cases a concentration of Echinarachnius blood that has 

 no effect on the fertilization of Echinarachnius eggs by its own 

 sperm will not give a single membrane or cleavage with heavy 

 Arbacia sperm suspension. Again, shed eggs of Echinarachnius 

 are superior to eggs cut out of the ovaries for cross fertilization. 

 Also, after thorough washing, eggs cut out of the ovaries and 

 fertilized with Arbacia sperm yield a higher per cent, of cleavage. 

 I interpret these facts as indicating that it is the presence of blood 

 that makes cross fertilization difficult. Blood thus acts in cross 

 fertilization as it does in straight fertilization ; the differences are 

 quantitative only. For Arbacia sperm enter Echinarachnius eggs 



