STUDIES OF FERTILIZATION 569 



contamination with the poisonous secretions of the epidermis, 

 especially of pedicellariae. It seemed at first that this objection 

 might be valid, for the period of my tests coincided with the 

 season of poor material when the blood was relatively free from 

 inhibitor. During this period, instead of following my earlier 

 practice of opening the animal r5.pidly and pouring out the blood, 

 I very carefully cut within the leathery peristome, avoiding all 

 possible contamination with epidermal secretions and removed 

 the blood with pipettes. This blood showed as a matter of fact 

 little inhibiting effect. However, with the return of animals in 

 good breeding condition, it was easy to show that the inhibitor 

 was contained in the blood itself; and not only this, but also that 

 epidermal secretions so far from increasing the inhibiting action 

 of the blood, actually decreased it, a matter to which we return 

 beyond. 



The next question was whether the inhibitor acted on the egg 

 alone, on the sperm alone, or merely by intervening in the reaction 

 between the two? In the experiments undertaken to answer 

 this question it was possible to show that the inhibitor certainly 

 does not act strongly on either the egg or the spermatozoa alone. 

 It is possible to collect eggs or sperm in filtered blood known to 

 have a strong inhibiting action, and, after considerable exposure, 

 to restore by washing nearly full fertilizing power, at least, to 

 both kinds of sexual elements. 



July 8: The blood used in this experiment allowed only 1 per cent 

 fertilization when diluted to 5 per cent with sea-water; it therefore con- 

 tained a great deal of the inhibitor. 



1. As regards the effect on eggs alone: 9:41 a.m. The eggs of one 

 female were placed direct from the ovary in some of this filtered blood. 

 Transfers of two drops of eggs to 10 cc. of sea-water plus one drop 1 

 per cent sperm were made as follows: a. 9:42, b. 9:50, c. 9:55, d. 10:03, 

 e. 10:23. About 60 per cent of each lot segmented. The blood carried 

 over would be about 0.625 per cent. Thus the inhibiting effect was 

 removed to a very great extent by washing. 2. In the case of sperm 

 collected in the same blood and used for fertilization at 1 minute, 12 

 minutes, 22 minutes, and 37 minutes, no indication of inhibition of 

 fertilizating power as compared with an identical series of controls 

 was observed. 



July 17: After 5 minutes' exposure to male blood sperm fertilized 20 

 per cent of the eggs ; control sperm 90 per cent, (sperm = 0.004 per cent) . 



