CONTENTS 



CHAP. PAGE 



VII. THE CYTOPLASMIC STRUCTURES IN SPERMATO- 



GENESIS AND OoGENESIS .... 9! 



The spermatozoon Its development Mitochondria 

 The acrosome and Golgi apparatus Oligopyrene and 

 apyrene spermatozoa Accessory cells The egg 

 Yolk and nutritive cells Egg membranes. 



III. FERTILISATION AND SEGMENTATION . . . in 



Entrance of spermatozoon Fertilisation membrane 

 and prevention of polyspermy Conjugation of nuclei 

 Segmentation Position of cleavage planes Centro- 

 lecithal segmentation Polyspermy. 



IX. PARTHENOGENESIS . . . . . .125 



Parthenogenetic eggs with one polar division Fer- 

 tilisation by second polar nucleus Parthenogenetic 

 eggs with two polar divisions Hymenoptera 

 Phasmidae Gall-flies False fertilisation Summary. 



X. ARTIFICIAL PARTHENOGENESIS .... 140 



Methods Theoretical explanations Comparison 

 with fertilisation Chromosomes and centrosomes 

 Artificial parthenogenesis in frogs Sex. 



XI. THE CYTOLOGICAL BASIS OF SEX-DETERMINATION 152 



Hymenoptera : haploid and diploid chromosome series 

 Heterochromosomes Idiochromosomes Life-cycle 

 of Aphids and Phylloxerans Hermaphroditism : Rhab- 

 donema Lepidoptera. 



XII. GERM-CELL DETERMINANTS .... 172 



Germ -plasm and germ-track Germ-cells of Ascaris 

 Of Sagitta Miastor Pole-plasm in other Insects 

 Oosoma of Litomastix Ectosomes of Copepoda 

 Oocyte of Dytiscus Sertoli cells Nature of germ-cell 

 determinants. 



XIII. THE THEORY OF THE INDIVIDUALITY OF THE 



CHROMOSOMES 188 



The hypothesis of individuality Evidence from 

 abnormal numbers Persistence of chromosomes in 

 the resting nucleus Differences of size and shape 

 Hybrids Differences of function of chromosomes 

 Microsomes as units. 



