MEDUSAE OF THE WORLD. 



THE HYDROMEDUSAE. 



INTRODUCTION. 



This work was commenced in 1892 at the suggestion of Dr. Alexander Agassiz 

 while I was a student in his marine laboratory at Newport. Dr. Agassiz's plan 

 was that we produce conjointly a work upon the Medusae, Siphonophora, and 

 Ctenophorae of the Atlantic coast of North America. In pursuance of this plan, 

 Dr. Agassiz sent me upon expeditions to Halifax, Nova Scotia; Eastport, Maine; 

 Charleston, South Carolina; and Tortugas, Florida. It was also my privilege to 

 accompany him as his assistant upon his expeditions to the Bahamas, and to the 

 coral regions of the tropical Pacific. During these years the majority of our 

 American species were captured and drawings of them made from life. 



The description of all of the then known American Atlantic forms was com- 

 pleted by me in 1900, but unfortunately the pressure of other and more important 

 work prevented the revision of the manuscript by Dr. Agassiz, and thus it remained 

 in the Museum of Comparative Zoology at Harvard University until 1904, when 

 Dr. Agassiz generously returned it to me with permission to publish it in any 

 manner whatsoever. Thus the original plan was reluctantly abandoned. 



During the four years that elapsed while the manuscript lay unstudied at 

 Harvard, new forms had been discovered along our coast; and Nutting and Hargitt 

 had published their papers upon the hydroids and medusae of the Woods Hole 

 region. 



It was necessary to thoroughly revise the manuscript, and in order to render it 

 of greater service, I have attempted to extend the original work to include descrip- 

 tions of all known forms of medusae from all parts of the world. This extension 

 was made possible through the generous establishment by the Carnegie Institution 

 of Washington of a Marine Research Laboratory at Tortugas, Florida. Many 

 forms were collected upon a cruise of the Carnegie Institution yacht Physalia 

 from Boothbay Harbor, Maine, to Tortugas, Florida; and new or interesting 

 medusae have been obtained each season upon excursions over the tropical Gulf 

 Stream, and among the Bahamas. My official position in connection with the 

 laboratory has afforded me every possible facility in time and opportunity tor tilt- 

 prosecution of these studies, and I can not too kindly express my sense of gratitude 

 to the executive officers of the Carnegie Institution tor their generous support. 



To Geheimrath Prof. Dr. Anton Dohrn, and to his able corps of associates at 

 the Stazione Zoologica, I am indebted for numerous kindnesses shown to me during 

 my visit to the laboratory at Naples from November to February, 1907 and 1908. 



I have also enjoyed full privileges of study in the libraries of the Museum of 

 Comparative Zoology at Harvard University; in the Boston Society of Natural 



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