INTRODUCTION xiii 



the Journal of the Royal Microscopical Society, and "Schwalbes 

 Jahresbericht" of Heidelberg, as well as in the Zurich Index or Zoo- 

 logical Record. He should also be instructed how to find the latest work 

 on a subject that he is seriously studying or is carrying out research 

 work upon. Also to find out who is doing such work or is interested 

 in it. 



The book does not pretend to stand as an authority or court of last 

 resort for the specialist in matters of general histology. In most cases 

 it does not carry the student into debated ground. It does attempt 

 to be a convenient teaching guide, to gain the interest of its readers and 

 to stimulate original thought. It is based on the course in "General 

 Histology" given in Princeton University by the senior author during 

 the last ten years. 



The writers have many to thank for favors and help in connection 

 with the work. Our colleagues in both universities have often aided us. 

 Dr. H. E. Jordan has made drawings for, revised, and written parts of 

 the work on the reproductive tissues. Professors A. H. Tuttle and 

 Wm. Libbey have read part of the text. 



We wish to thank the United States National Museum and the 

 United States Fish Commission for some rare materials given through 

 the courtesy of their officials. Also the Carnegie Institution for much 

 material collected at the Tortuges Laboratory through the kindness 

 of Dr. A. G. Mayer. The writers are most appreciative as well as proud 

 of these American institutions, which are of such continued aid to science. 



Mr. and Mrs. Alfred Mitchell most generously provided the oppor- 

 tunity to collect valuable material in Jamaica, which is rich in many rare 

 forms. Dr. F. R. Lillie of Chicago sent us Unio material at a time of 

 the year when it could not be collected, and the Yale Museum furnished 

 us with some rare Schizopods. 



We wish to extend special thanks to Mr. Charles A. McAlpin of 

 Princeton for his great help in providing the Zoological department of 

 the university with quantities of new and old books, back files of periodi- 

 cals, and other literature. His generosity is one of the factors which 

 has made it possible to do this work in Princeton. 



