2 MEDUSvE OF THE WORLD. 



History; the American Museum of Natural History; Columbia University, the 

 National Museum at Washington, and the Museum of the Brooklyn Institute of Arts 

 and Sciences. Through these facilities I have been enabled to review nearly all 

 of the published works upon medusae, but the review of literature can not pre- 

 tend to completeness for 1907 and 1908, although all papers of those years which 

 the author could discover are recorded. 



Moreover, Profs. William K. Brooks and Louis Murbach have been so kind 

 as to lend some of their original drawings, which are reproduced in this work, and 

 the following gentlemen have generously granted permission for the reproduction 

 of figures from their published works, thus enabling us to present text-figures of 

 many forms which would otherwise have been represented merely by descriptions: 

 Dr. Alexander Agassiz, Director of the Museum of Comparative Zoology at Harvard 

 University; Dr. Henry B. Bigelow, of Harvard; Dr. R. P. Bigelow, of the Massa- 

 chusetts Institute of Technology; Prof. Edward T. Browne, of the University of 

 London; Prof. Dr. Carl Chun, of Leipzig; Prof. Dr. S. Goto of Tokyo; 

 Geheimrath Prof. Dr. Ernst Haeckel, of Jena; Prof. C. W. Hargitt, of Syracuse 

 University; Prof. Dr. Cl. Hartlaub, of Helgoland; Prof. W. C. M'Intosh, of Aber- 

 deen University; Prof. Dr. Otto Maas, of Miinchen; Prof. C. C. Nutting, of Iowa; 

 Prof. Henry F. Perkins, of Vermont; and Prof. Dr. Ernst Vanhoffen, of Kiel. 



I have always felt that each working naturalist owes it as a duty to science to 

 produce some general systematic work, and this has been an actuating motive 

 in the production of this book. But chiefly have I been moved to the task through 

 respect for the wishes of my generous friend and master in science, Alexander 

 Agassiz. Nor can one remain insensible to the rare grace of form and delicate 

 beauty of color of these creatures of the sea, associated as their study is with mem- 

 orials of the labors of a host of distinguished naturalists. Dry though these pages 

 must be to the reader, to the writer they are replete with memories of the ocean 

 in many moods, of the palm-edged lagoons of coral islands sparkling in the tropic 

 sun, of the cold, gray waters of the northern sea bestrewn with floating ice, of days 

 of withering calm in the heat of the torrid zone, and of adventure in the hurricane ; 

 all centering around the absorbing study of the medusa?. Love, not logic, impels 

 the naturalist to his work. 



This book attempts to present a new classification of the medusae. With every 

 respect for Haeckel's great work, it has appeared to me that its subdivisions are 

 often too precise to be convenient, and too artificial to accord with nature. More- 

 over, many of Haeckel's genera are founded upon intergrading characters, and are 

 thus imperfectly separated. The young of many medusae appear in one genus, 

 and the adults in another. The aim of Haeckel's system is to emphasize distinctions, 

 whereas my aim is to indicate relationships. I therefore attempt to separate genera 

 upon positive, not upon relative, distinctions. For example, if we define one genus 

 as having a narrow manubrium (Margelis), and another as having a wide manu- 

 brium (Boiigamvillta), we must either institute a third genus for newly-discovered 

 medusae with manubria of moderate width or place them doubtfully in one or the 

 other of the genera of the extreme members of the series. 



On the other hand, if we define one genus as having eight tentacles, and 

 another as having nine or more tentacles, there can be no confusion between them, 

 for the difference, although slight, is positive and numerical, not qualitative and 

 intergrading. 



I have not described hydroids which do not produce free-swimming medusae, 

 although I grant it is wholly illogical to admit Podocoryne into a system which 

 excludes Hydractmia, or to include only those species of Stylactis which produce 



