Introduction [ 5 



that Barkley (1939, 1949) and Rothmaler (1948) maintain a system of kingdoms 

 which differs from this in a single significant detail. 



Assuming that this system is tenable as a matter of reason, it will nevertheless not 

 be accepted among taxonomists unless they have some knowledge of what it means 

 in detail. No person is called upon to recognize the kingdoms Mychota and Protoc- 

 tista until systems of their subordinate groups are available. The bulk of the present 

 work consists of such systems. Complete systems of divisions or phyla, classes, and 

 orders are presented. Groups of lower rank are presented in part, as examples. As a 

 matter of facility, the groups of lower rank are presented more fully in the smaller or 

 better known groups than in the larger or more obscure. 



The preparation of this work has taken more than ten years. In the course of it I 

 have received much help. Among those who have answered queries, or who have in 

 various drafts scrutinized the whole work or parts of it for faults of every degree of 

 significance, are Dr. G. M. Smith of Stanford University; Dr. A. S. Campbell of St. 

 Mary's College; Dr. Herbert Graham, formerly of Mills College; Dr. Lee Bonar, Dr. 

 G. L. Papenfuss, and Dr. H. L. Mason of the University of California at Berkeley; 

 Dr. E. R. Noble of the University of California at Santa Barbara; and Dr. H. C. Day 

 of Sacramento Junior College. The counsel of E. B. Copeland has not been withheld. 

 It is a matter of grief that two distinguished zoologists of the University of California, 

 Dr. S. F. Light and Dr. Harold Kirby, have passed away during the long course of 

 this work; as have two colleagues who were my closest friends, Dr. H. J. Child and 

 Dr. C. C. Wright. 



The portrait of Haeckel which is my frontispiece is used by permission of Macrae 

 Smith Company, Philadelphia. Two figures of Chrysocapsa are used by permission 

 of the Cambridge University Press. Numerous figures have been taken from the 

 Archiv filr Protistenkunde with the gracious permission of Prof. Dr. Max Hartmann. 



We do well to realize our indebtedness to libraries and librarians. To a great extent, 

 this work has been made possible by the unstinted hospitality of the Biology Library 

 of the University of California at Berkeley. 



Two statements appear regularly in prefaces; they are of truths which are strongly 

 impressed upon authors. In the first place, those who have given help have made the 

 work better; the author alone is responsible for deficiencies. The foregoing list of 

 good friends and good scholars does not claim them as proponents of the thesis of 

 this work. 



In the second place, the work is not offered as perfect or nearly so. The scholar in 

 a strictly limited field may become master of the available knowledge. One who at- 

 tempts studies in a broad field realizes that he is dealing with many subjects of which 

 others know far more than he; that he has not wrung dry the existing literature; that 

 some of the problems which puzzle him will be solved if he will wait a little longer. 

 His colleagues have a right to raise these matters as criticisms. But surely, it is not 

 desired that studies in broad fields be never attempted or indefinitely delayed. 



A matter which is particularly likely to arouse criticism is that of the names which 

 are here applied to the groups. The principles according to which this has been done 

 are set forth in the following chapter. I beg my colleagues, in dealing with this chapter 

 and with the names subsequently applied, not to imagine that I have acted without 

 grave thought. I have decided, that as in classification, so also in nomenclature, I 

 should set before the community of biologists an experiment in the application of 

 principles; among which principles there are surely some whose strict application 

 will be to the good of our science. 



