516 FRANK R. LILLIE 



IV. Agglutination phenomena and reactions of spermatozoa to egg-secre- 

 tions 548 



1. Introduction 548 



2. Initial experiment 550 



3. Ova alone produce the agglutinating substance 552 



4. Fixation of the agglutinin by spermatozoa 554 



5. Nature of the effect on the sperm 555 



6. Thermo-resistance of the agglutinin 557 



7. Fertilizing power of agglutinated sperm 558 



8. Conditions of formation of the agglutinin by the eggs 559 



9. Hetero-agglutination and the question of specificity 5C1 



10. Interpretation of some phenomena of normal fertilization of 



Nereis 567 



11. Summary: Part IV 568 



V. Discussion 569 



Literature cited 574 



I. INTRODUCTION 



The earlier studies of this series dealt exclusively with Nereis 

 and concerned the cortical changes of the egg, partial fertiliza- 

 tion, the morphology of the normal fertilization and the fertilizing 

 power of portions of the spermatozoon. They yielded certain 

 positive results which I need not review, but they had convinced 

 me that other methods than the ones usually in vogue, includ- 

 ing the methods of artificial parthenogenesis, are needed for a 

 closer approach to some fundamental problems of fertilization. 

 Some incidental observations drew my attention to the study of 

 the behavior of the spermatozoa, and investigation of the subject 

 soon showed that the reactions of these minute active reproduc- 

 tive elements might furnish evidence of considerable significance. 

 This study was begun in the summer of 1911 and continued 

 throughout the summer of 1912 at the Marine Biological Labora- 

 tory. 



With the publication of Loeb's first study on artificial partheno- 

 genesis the study of fertilization entered upon a new phase which 

 has not yet run its entire course. The tendency during this 

 phase of investigation has been to regard initiation of develop- 

 ment as the fundamental problem of fertilization; and the aim 

 has been to discover the way in which the spermatozoon induces 

 development of the egg. Hence the term 'chemical fertihzation' 



