PREFACE 



THIS book is intended for use in connection with college and university 

 courses in the biological sciences. It is not a new edition of the 

 author's "Introduction to Cytolog.y," which was designed to serve both 

 as a reference work, of which plant cj^tology was in need, and as a general 

 textbook. This is a textbook only. Although it deals again with 

 various principal topics of the older work and uses some of its illustrations 

 along with manj^ new ones, the present text is much briefer, simpler in 

 treatment, and, it is hoped, better adapted to the needs of students whose 

 curiosity concerning cytology has been newly aroused in elementary 

 courses in animal and plant science. The title of the oldei- book, in fact, 

 might well have been reserved for this one. Where subjects not essential 

 to an introductory^ treatise are included, it is not with the thought that 

 they should be mastered now, but rather to indicate further fields of 

 inquiry open to students of cytology. 



No attempt has been made to maintain the connection between 

 statement and source characteristic of the "Introduction to Cytology." 

 Each chapter has, however, been provided with a short list of books and 

 recent papers for the use of those who wish to begin an examination of 

 the literature, but to avoid distraction the text has been left unencum- 

 bered by specific references to them. Anyone who prepares a book of 

 this kind knows well that he is presenting mainly the work of authors 

 whose names do not appear on the title page, and he only trusts that he 

 does this with accuracy and fairness. 



The selection, arrangement, and treatment of the various topics 

 have been determined by experience in cytology courses having a geneti- 

 cal and phylogenetical bearing. In the interest of simplicity, emphasis 

 has been placed upon "typical" cytological phenomena. Care has been 

 taken, however, to suggest the great diversity in cytological constitution 

 and behavior exhibited by plants and animals and to indicate the many 

 uncertainties in a field where growth is rapid and opinions are subject to 

 change with new evidence. It is unfortunate that the terminology 

 could not be further simplified without impairing the usefulness of the 

 book for those preparing to consult the literature. As every experienced 

 teacher of natural science is aware, the student's actual knowledge of the 

 subject is gained primarily- in the field and laboratory. It is there, 

 by thoughtful observation and discussion, that his comprehension is 



