PREFACE ix 



NOTE 



Less than two months after the completion of the text of this book 

 the author has received copies of the two new English works on cytology : 

 W. E. Agar's Cytology, With Special Reference to the Metazoan Nucleus and 

 L. Doncaster's An Introduction to the Study of Cytology. Both deal 

 almost exclusively with animal cytology, the first being valuable for 

 its account of chromosome behavior in animals, and the second for its 

 discussions of gametogenesis, fertilization, parthenogenesis, and sex- 

 determination. These works, together with the botanical portions of 

 the present volume, should make an acquaintance with the general field 

 of cytology much more readily attainable. 



