H. M. FucHS 243 



the last column it is seen that all these eggs had already been selt'ed. 

 Again in Exp. 4, although the treated eggs show for both fertilizations 

 lower percentages than the untreated, in the previously treated eggs 

 the second percentage is higher than the first. This is, however, really 

 due to the presence in the treated eggs of 28 '/^ already self-fertilized. 



When the presence of self-fertilized eggs in the lots which have 

 been treated with "own" sperm is allowed for, the fall in cross-fertiliza- 

 tion percentages of the latter is even more marked than appeared at 

 first sight. This might be due to one of two causes. Either the 

 presence of "own" spermatozoa calls forth a reaction on the part of the 

 eggs hindering the entrance of the former, and also — although to a 

 much lesser degree — hindering the entrance of "foreign" spermatozoa: 

 or the presence of the small amount of sperm-suspension which is 

 necessarily carried over with the drop of eggs removed for cross-fertili- 

 zation itself inhibits the "foreign" spermatozoa. For spermatozoa in 

 the vas deferens are motionless, and this must be due either to the 

 absence of sea-water, or to the presence of a substance inhibiting move- 

 ment. If the latter exists, it must be present in a dilute form in the 

 suspension of "own" sperm, and might conceivably act on the "foreign" 

 spermatozoa when these are added to the drop of eggs taken from this 

 suspension. In order to test whether this is the explanation of the 

 diminished cross-fertilization pei'centages of the treated eggs, or whether 

 the latter have really been altered in their capacity for cross-fertilization 

 by their sojourn in "own" sperm, further experiments were made. 

 Before being cross-fertilized, the treated eggs were thoroughly washed 

 in a comparatively large volume of water. 



As in the previous experiments, the eggs of each individual were 

 divided into two lots, and placed respectively in water and in opalescent 

 "own" sperm suspension. After a definite interval (10 mins. in Exps. 1 

 and 2; 15 mins. in Exp. 3) Ice. of "own" sperm containing eggs was 

 removed to 100 cc. of plain water in a finger-bowl, in which the eggs 

 were allowed to settle in order to remove excess of sperm. A definite 

 quantity of "foreign" sperm-suspension (given in Table IX) was pipetted 

 into each of two dishes containing 10 cc. water. These were then 

 poured on to separate approximately equal quantities of eggs (1) from 

 plain water, (2) from the finger-bowl. 



In these experiments fertilizations were not made at different 

 intervals of time as in the former ones, but each was made double, two 

 different amounts of sperm being used. The results of the experiments 

 are recorded in Table IX. 



i«— 2 



