2 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



Scientific controversy is so unprofitable that I shall try to make it as 

 subordinate as possible, that the reader may devote all his attention to 

 the life-history of salpa without interruption at every point where my 

 own observations confirm or contradict the statements of others. 



The story of the life-history of salpa is most interesting, but it is 

 complicated and difficult to tell in simple words, even after it has been 

 stripped- of all which is not essential, and I am sure that I shall promote 

 the interest of my readers by strict adherence to the unity of my descrip- 

 tion. 



I shall therefore give, in the first place, a continuous, uninterrupted 

 account of the subject, and shall reserve the discussion of disputed points 

 for later chapters. 



I know that I have built upon a foundation which has been laid by 

 others, and that many of the facts have been the common property of 

 naturalists for many years, but truth and error are so closely bound 

 together in the literature of the subject that it is not possible to give to 

 each author the credit which is his due without entering into adverse 

 criticism at the same time, and as the history of our knowledge of Salpa 

 has been reviewed over and over again, it does not seem necessary to 

 enter into it here. 



The home of the salpas is so remote from common observation that 

 few persons except naturalists have a true conception of their scientific 

 interest, or of their importance in the economy of the sea, although they 

 occupy a prominent place in the mind of every one who has enjoyed 

 the pleasure of studying the floating fauna of the open ocean, and is thus 

 enabled to call up a mental image of pelagic life as a whole. 



The older naturalists who explored the ocean in sailing vessels, when 

 calms gave leisure for studying its wonders, found in them an unfailing 

 subject for fascinating and delightful research. They are seldom found 

 near the shore, however, and as they are so transparent that they are 

 scarcely visible from the deck of a modern steamship, they are little 

 more than a name to most of the naturalists of our own day; but to 

 the student, even the name, salpa, itself calls up a long list of famous 

 naturalists and explorers. 



Among them is the friend of Linnaeus, Peter Forskal, who lost his 

 life while exploring Arabia in 1774. His description of the animals 

 which he had observed in his journey to the East was edited and pub- 

 lished by his fellow-explorer, Niebuhr ; and in it eleven forms of salpae, 

 which he had observed and studied in his voyage through the Mediter- 



