LARVAE OF ARBACIA PUNCTULATA 



419 



brane-formation (e), while the eggs from the concentrated 

 supply, fertilized with diluted sperm-suspension gave entirely 

 negative results (/). The sperms, although slightly activated, 

 were unable to penetrate even into freshly extruded eggs (i). 

 In solution e, the small percentage that developed were of low 

 vigor, were smaller than the control, and lived only three days. 

 The eggs from the diluted stock fertilized with fresh sperm 

 (h) also showed lowered vitality, so that before 120 hours all 

 were dead. 



In another series of experiments done in the same way, the 

 sperm was so active at the end of 24 hours and the percentage 

 of fertilizations was so high, that the germinal products were 

 kept for several days and the experiments repeated. The 

 following results were obtained: 



Owing to the lack of time, the measurements of these larvae 

 were not taken, but the cultures were kept for several days and 

 the vigor of the resulting individuals observed. No reduction, 

 in size in the later fertilization was observable, but as in the 

 previous experiment, this decrease would probably be so small 

 that it could be determined only by actual measurement. 



All from the 24 and 48 hour fertilizations were apparently 

 as vigorous as the control which was started immediately after 

 extrusion. After 72 hours, however, a lessened vitality was 

 observable, but only when the sperm had been diluted. In these 

 cultures the death-rate was so much higher that comparatively 

 few attained the pluteus stage. After 96 hours, a lessened vigor 

 was apparent in all the solutions. Normal plutei were formed 

 in a and h, but in c the cleavage was irregular, and few normal 

 individuals resulted. 



