STUDIES OF FERTILIZATION 561 



worked out in this experiment; however, Herbst ('00) found in 

 his experiments on superposition of f ertiUzation on parthenogenesis 

 that eggs overexposed to butyric acid could be fertihzed, though 

 incompletely. 



Ninety-five per cent of the A eggs showed no evidence of cytol- 

 ysis on the next day, beyond the membrane formation. They 

 were intact and healthy looking. The remaining 5 per cent were 

 fragmented, or segmsented, into about 16 to 32 cells, within the 

 membrane and appeared cytolyzed. In the B eggs the agglutina- 

 tion had disappeared, and there was about the same percentage 

 of dividing eggs as in ^, but in absence of a membrane the cells 

 were breaking apart. 



A similar experiment on August 25 gave the same result, viz.^ 

 disappearance of the agglutinating substance after membrane 

 formation by butyric acid. 



Summarizing this section, then, we may say that eggs are 

 rendered incapable of fertilization by methods that eliminate 

 the sperm-agglutinating substance whether (a) the substance is 

 lost, as in some eggs after repeated washings, or (b) fixed by 

 previous fertilization, or (c) fixed by parthenogenetic methods. 

 The conclusion is therefore justified that the agglutinating sub- 

 stance is necessary for fertilization. 



8. SUMMARY OF PART III SPERMOPHILE GROUP OF THE FERTILIZIK 



After considering a method for determining the quantities of 

 fertilizin produced by ova of Arbacia, we demonstrated (1) that 

 unfertilized eggs in sea-water produce this substance in extremely 

 large quantities. The secretion begins presumably in the ovary 

 with breaking of the germinal vesicle. Although the jelly is sat- 

 urated with it and liberates it by solution in the sea-water, eggs 

 without jelly continue to secrete if for three days, at least, during 

 repeated washings, or as long as they remain alive. (2) The 

 spermatozoa of Arbacia possess extreme avidity for the fertilizin 

 and bind it in definite amounts. In the case of fresh active sperm 

 the binding is evidenced by reversible agglutination of the sper- 

 matozoa. But a stale sperm suspension may also bind it, although 



