CHAPTER I. 

 INTRODUCTORY. 



Most of the material for the researches on which this memoir is based 

 was gathered and preserved at sea, at various points upon the eastern and 

 western coast of the United States, by the vessels of the United States 

 Fish Commission, under the direction of Marshall M'Donald, the Com- 

 missioner of Fisheries. 



As the schooner Grampus was engaged during the summer of 1888 

 in work which gave, incidentally, an excellent opportunity for pelagic 

 exploration, the commissioner invited me to avail myself of the advant- 

 age, and I owe to him the pleasure of a cruise in the Gulf Stream under 

 conditions which were most favorable for studying its floating fauna. 



I have also received from the commissioner, from time to time, col- 

 lections of salpoe which have been gathered, under his direction, at various 

 localities near our coast. These specimens have been preserved for 

 microscopic research, according to approved methods, by Professor Wm. 

 Libbey, Professor L. A. Lee and Mr. K. P. Bigelow, and I am indebted to 

 these gentlemen for many valuable additions to my collection. 



My thanks are also due to the National Academy of Sciences for a 

 grant of money from the "Bache" fund, to aid me in the prosecution of 

 this research ; and to the Trustees of the Johns Hopkins University for 

 the opportunity to study living salpae at many points upon our coast, 

 and for the provision which they have made, from the funds of the Uni- 

 versity, for the publication of this memoir. 



As I enter upon the preparation of this account of a research which 

 has been, up to this point, an unfailing source of pleasant interest, I am 

 confronted by the disagreeable prospect of inevitable controversy ; and 

 all my pleasure is destroyed by the thought that nearly every one of 

 my statements will contradict the published statements of some one 

 among the numerous writers on the subject. 



