28 FRANK R. LILLIE. 



and takes place probably at the time of breaking down of the 

 germinal vesicle. 



Loeb's contention that the agglutinating substance is merely 

 dissolved chorion therefore does not hold for Arbacia. With 

 this his argument against my fertilizin theory also falls: "More- 

 over if it should turn out that the substance which is responsible 

 for the cluster formation is identical with the substance which 

 Lillie calls "fertilizin," which is very likely the case, Lillie's 

 theory becomes untenable, since this substance does not, in all 

 probability, originate from the egg, but from the chorion and 

 since there is, as we have seen, no connection between the presence 

 of this substance and the power of the eggs of being fertilized" 

 (pp. 136-137— Loeb, '14). 



In this statement Loeb sums up the essentials of his criticism ; 

 since I have shown that "cluster formation" is true agglutination 

 (which Loeb now admits), and that the agglutinating substance 

 (my fertilizin) is not dissolved chorion but a true secretion of 

 the eggs which continues to be produced after the chorion is 

 removed, the entire stated criticism becomes ineffective. There 

 is a connection between the presence of this substance and the 

 power of the eggs of being fertilized: the substance can first be 

 demonstrated at the time that the power of being fertilized first 

 arises, viz., after breakdown of the germinal vesicle; it can be 

 demonstrated as long as eggs retain the power of being fertilized, 

 whether the chorion be removed or not, and it disappears ab- 

 solutely after fertilization, as I showed in my previous paper 

 (study VI, p. 553, 1914). 



3. Other Criticisms. 

 Another objection raised by Loeb is that "the supernatant 

 sea-water of the eggs of Strongylocentrotus franciscanus will not 

 induce cluster formation of the sperm of Strongylocentrotus 

 purpuratus: yet the latter sperm fertilizes the eggs of francis- 

 canus," from which he argues that the fertilizin of Strongylo- 

 centrotus franciscanus can not be necessary for the fertilization of 

 its eggs. An error in logic is involved here ; agglutination of sperm 

 is merely an indicator of the presence of a certain substance, 

 which is none the less present in franciscanus even if purpuratus 



