Vlll CONTENTS. 



PAGE 



VIII. " Body " versus reproductive cells, and the continuity 

 of the latter. 

 Owen. 

 Haeckel. 

 Rauber. 

 Brooks. 

 Jager. 

 Galton. 

 Nussbaum. 

 IX. Weismann's theory' of the continuity of the germ-plasma. 



CHAPTER VIII. 



The Egg-Cell or Ovum ... _ 92-102 



I. Structure of ovum — 



Cell substance and protoplasm. 

 Nucleus and chromatin. 

 II. Growth of ovum — 



Transition from amoeboid to encysted phase. 



III. The yelk — 



Its threefold mode of origin. 



Its diffuse, polar, or central disposition. 



Resulting influence on segmentation. 



IV. Composite ova. 

 V. Egg-envelopes — 



(a) From ovum itself. 



(b) From surrounding cells. 



(c) From special glands. 

 VI. Birds' eggs — 



Concrete illustration of facts and problems. 

 VII. Chemistry of the ovum — 



Its capital of anastates. 

 VIII. Maturation of ovum — 



Occurrence, formation, history of polar globules ; 

 parthenogenetic ova. 

 IX. Theories of polar globules — 



1. Minot, Balfour, Van Beneden, &c. 



2. Biitschli, Hertwig, Boveri, &c. 



3. Weismann. 



CHAPTER IX. 



The Male-Cell or Sperm ------ 103-110 



I. General contrast between sperm and ovum — 



An index to contrast between male and female. 

 II. History of discovery' — 



(a) Hamm and Leeuwenhoek. 



(b) Animalculists. 



(r) Classed as Entozoa or parasites. 



(d) Kolliker's demonstration of cellular origin. 



