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THE AMERICAN NATURALIST 



[Vol. XLIX 



To this Lillie replies that perhaps the sperm of pur- 

 puratus is not so delicate an indicator for agglutinin as 

 the sperm of Arbacia— but as long as the agglutination 

 reaction is the only test for the presence of fertilizin in 

 the egg, such an answer begs the question. 



From the fact that the power of agglutinating the sperm 

 is lost if the egg of purpuratus is deprived of its jelly by 

 acid treatment the writer drew the conclusion that in this 

 egg the ' ' fertilizin ' ' does not come from the unfertilized 

 egg but only from its jelly and that this was contrary to 

 Lillie 's assumption. To this Lillie 31 replied by pointing 

 out that the immature eggs of Arbacia do not give the ag- 

 glutination reaction while the mature Arbacia egg gives 

 the reaction very powerfully, and that we must conclude 

 from this that the ' 1 fertilizin " contained in the jelly 

 comes from the egg and is given off during the period of 

 the maturation divisions (the latter statement, however, 

 is after all only an assumption though a probable one). 

 But this does not meet the question at issue, namely that 

 in the egg of purpuratus at the time of maturity the fer- 

 tilizin which is given off is contained exclusively in the 

 jelly and not in the egg, as it should be if the presence 

 of fertilizin in the egg were a prerequisite for its ability 

 of being fertilized. It is true that if we repeat this ex- 

 periment in the egg of Arbacia we find that after the re- 

 moval of the jelly by HC1 a trace of the agglutinating sub- 

 stance may still be given off by the egg, although little in 

 comparison with that given off by the jelly. But this 

 does not alter the facts as they are found in the egg of 

 purpuratus. 



As far as the two other proofs of Lillie are concerned, 

 we have already touched upon them in the previous parts 

 of this paper. The fact that the fertilized eggs of Ar- 

 bacia (and of purpuratus) cease to give the agglutinin 

 reaction is due to the loss of the jelly on the part of the 

 fertilized egg to which in Arbacia should be added the 

 fact that some of the material of the cortical layer is given 



3i Lillie, Biol. Bull., XXVIII, 18, 1915. 



