INITIATION OF DEVELOPMENT IN EGG OF ARBACIA. 



417 



B. 



We may now consider those experiments which reveal that dur- 

 ing the later half of the season the shed eggs of Arbacia are of 

 low fertilization capacity, whereas eggs taken from the ovaries are 

 of high fertilization capacity. 







THE EXPERIMENTS. 



(a) July 23, 8:00 A.M. Portions of shed eggs from 12 Ar- . 

 bacia inseminated in turn. All poor; not more than 10 per cent, 

 membranes in any lot. 



Ovaries from these same females chopped up separately in sea- 

 water and eggs strained out. Eggs inseminated. Fine mem- 

 branes (average: around 96 per cent.). 



This experiment scarcely needs comment. The eggs that exude 

 through the genital pores are inferior to those procured by cutting 

 up the ovaries in sea-water. And this was found to be true from 

 July 23 to the end of the season in 107 out of 125 females tested 

 on this one point alone. 



(b) July 25, 9:00 A.M. 9 females opened. Eggs exude 

 through genital pores into dry dishes. 250 c.c. of sea-water added 

 to each lot of eggs. Samples from each inseminated. No mem- 

 branes in Nos. i, 2, 4, 6, and /. 80 per cent, membranes in No. 3. 

 Nos. 5, 8, and 9 give 18, 6, and 14 per cent, membranes, respect- 

 ively. Effect not due to sperm for inseminations were next made 

 in each case with sperm from 7 different males with essentially the 

 same results. 



Eggs removed from these 9 females inseminated in turn. Fine 

 membranes ; average around 98 per cent. 



To offset any criticism that these results might be due to pres- 

 ence of blood with sperm, great care was exercised in opening all 

 animals. During several days, for example, all instruments were 

 sterilized before using by heating red hot in order to destroy any 

 adherent blood. If animals cut proved to be males, they usually 

 exuded clean sperm into the dry watch glasses. In many cases 

 the males shed spontaneously. Thus only uncontaminated sperm 

 was procured. In addition, sperm from several males was used 

 as mentioned in the experiment cited above. Finally, the results 

 of inseminating the eggs taken from the ovaries would seem to 



