vili PREFACE 



part of the ground already so well covered by Hertwig.^ This book 

 does not, however, in any manner aim to be a treatise on general 

 histology, or to give an exhaustive account of the cell. It has rather 

 been my endeavour to consider, within moderate limits, those features 

 of the cell that seem more important and suggestive to the student 

 of development, and in some measure to trace the steps by which our 

 present knowledge has been acquired. A work thus limited neces- 

 sarily shows many gaps ; and some of these, especially on the botani- 

 cal side, are, I fear, but too obvious. On its historical side, too, the 

 subject could be traced only in its main outlines, and to many 

 investigators of whose results I have made use it has been impossible 

 to do full justice. 



To the purely speculative side of the subject I do not desire to 

 add more than is necessary to define some of the problems still to be 

 solved ; for I am mindful of Blumenbach's remark that while Drelin- 

 court rejected two hundred and sixty-two "groundless hypotheses" 

 of development, " nothing is more certain than that Drelincourt's 

 own theory formed the two hundred and sixty-third."^ I have no 

 wish to add another to this list. And yet, even in a field where 

 standpoints are so rapidly shifting and existing views are still so 

 widely opposed, the conclusions of the individual observer may have 

 a certain value if they point the way to further investigation of the 

 facts. In this spirit I have endeavoured to examine some of the more 

 important existing views, to trace them to their sources, and in some 

 measure to give a critical estimate of their present standing, in the 

 hope of finding suggestion for further research. 



Every writer on the cell must find himself under a heavy obliga- 

 tion to the works of Van Beneden, Oscar Hertwig, Flemming, Stras- 

 burger, and Boveri ; and to the last-named author I have a special 

 sense of gratitude. I am much indebted to my former student, 

 Mr. A. P. Mathews, for calling my attention to the importance of 

 the recent work of physiological chemists in its bearing on the 

 problems of synthetic metabolism. The views developed in Chap- 

 ter VII. have been considerably influenced by his suggestions, and 

 this subject will be more fully treated by him in a forthcoming work ; 

 but I have endeavoured as far as possible to avoid anticipating his own 

 special conclusions. Among many others to whom I am indebted 

 for kindly suggestion and advice, I must particularly mention my 

 ever helpful friend, Professor Henry F. Osborn, and Professors 

 J. E. Humphrey, T. H. Morgan, and F. S. Lee. 



In copying so great a number of figures from the papers of other 



1 Henneguy's Lemons sur la cellule is received, too late for further notice, as this volume 

 is going through the press. 



2 Allen Thomson. 



