H. M. FucHS 253 



been the earliest in the crosses, although that of Cja had been the 

 latest. There seems to be little or no correspondence between the 

 relative rapidity of segmentation and the subsequent development. 



The larvae of each cross which settled down on the first, on the 

 second and on the third day after hatching were reared separately. 

 Those from the first and second days developed equally well, but those 

 from the third much worse in each case. 



Besides the two experiments given in Tables XII and XIII, a con- 

 siderable number of other similar ones were carried out. All agreed in 

 showing that the early segmentation of self-fertilized eggs is little if at 

 all slower than of cross-fertilized, but that the larvae of the former 

 hatch out somewhat later. Very frequently, however, the larvae from 

 the self-fertilizations do not fix themselves at all, but die off. When 

 they do settle down they fail to develop further, perishing in the course 

 of a few days. One exception only was found to the last statement. 

 A self-fertilized culture {Aja) made on June 20th gave a low percentage 

 of fertilization. Some of the larvae fixed themselves, and on June 22nd 

 — more than a month later — four individuals were still alive. They 

 had attained the length of 1 cm. and appeared to be very healthy. 

 Young from both of the cross-fertilizations, Ajh and Bjh, however, grew 

 nuich moi'e rapidly. 



VI. Summary of Experimental Results. 



(1) A greater concentration of sperm is usually necessary to bring 

 about any self-fertilization than would cross-fertilize 100°/^ of "foreigTi" 

 eggs. 



(2) An increase in the concentration of the sperm-suspension causes 

 an increase in the number of eggs self-fertilized. 



(3) The proportion of eggs self-fertilized increases with the length 

 of time the eggs and sperm have been in sea-water before fertilization 

 is effected. The percentages rise to a maximum and then decrease 

 again, the time of the maximum being different for each individual. 

 The subsequent decrease in the percentages is probably due to a falling 

 off of the "fertilizing power" of the sperm-suspension. It cannot be 

 determined whether the rise in self-fertilization percentages is due to a 

 change in the eggs or in the sperm. The cross-fertilization percentages 

 decrease as the time the eggs and sperm lie in sea-water before fertili- 

 zation increases. 



