IV INTRODUCTION. 



When this volume was begun, it was not intended to include so large a field within its 

 scope, but unexpected delays have brought us to a time when there is an entire discontinu- 

 ance of deep-sea work, and when the final ichthyological results of all past expeditions 

 have been published. 



In 1885 Prof. Collett, of the University of Christiania, published a volume upon the 

 fishes of the Norwegian North Sea Expedition. In 1887 Dr. Gunther, of the British Museum, 

 published his great work on " The Deep-Sea Fishes of the Challenger Expedition ". In 1888 

 Dr. Yaillant, of the Museum of Natural History in Paris, reported upon the Deep-Sea Fishes 

 of the Travailleur and Talisman Expedition, and in the same year Mr. Alexander Agassiz 

 presented his admirable "Contributions to American Thalassography", in which, for the 

 first time, were presented in compact form the results of the ichthyological work of the Coast 

 Survey and the Fish Commission. 



These four magnificent works, together with the various short papers since published 

 by American and Scandinavian naturalists and by Mr. S. Alcock upon the deep-sea fishes of 

 India, relate to a group of animals concerning which, until recently, naturalists knew almost 

 nothing. 



The study of oceanic ichthyology is still in its infancy and yet many very remarkable 

 results have been obtained. Although not more than 600(f) different kinds of lishes have 

 been obtained from the depth of 1,000 feet and more, it would appear that a very good 

 general idea of the character of the fauna has already been acquired. This is indicated 

 by the fact that fishes are constantly being rediscovered in the most remote localities. A 

 form obtained by Lowe in Madeira in 1870 was rediscovered by us off the New England 

 coasl in 1881, and by German naturalists in the Japanese Sea in L879, by the Blake near 

 Barbadoes in 1880, and a year or two later jff the coast of Soudan. Several previously 

 known only from New Zealand have been obtained by the Fish Commission off the New 

 England coast, and some of our own genera and species have lately been discovered in tin- 

 Bay of Bengal. 



Although the capture of certain individual forms in widely remote localities in the 

 oceanic abyss might l>e interpreted to mean that the field has been somewhat fully 

 explored, and that it is now being gone over a second or third time, such an interpretation 

 would be misleading. Our knowledge of abyssal life is still exceedingly imperfect. New 

 species and genera are obtained every time the nets are lowered to the bottom in an 

 untried spot. Very many forms have been taken in only one locality, and are represented 

 in the museums by unique specimens, so that the ichthyologist has not material enough to 

 enable him to study the structure of the organisms to which he has given a name. Then, 

 too, the appliances for the capture of the fishes of any region, especially those which are 

 believed to live suspended in the middle strata of mid-ocean, are so imperfect, and the like- 

 lihood is great that there are many forms so organized that they can not well be taken 

 by small slow-moving nets, that naturalists will surely fall into error if they suppose 

 themselves in possession of anything like an adequate equipment for a final study of the 

 subject. 



It seems probable that there are many inhabitants of the depths which are too swift, 

 too wary and cunning, or too large thus to be taken. It cannot be doubted, for example, 

 that somewhere in the sea, at an unknown distance below the surface, there are living 

 certain fish-like animals, unknown to science and of great size, which come occasionally to 

 the surface and give a foundation to such stories as those of the sea serpent. 



To appreciate the meager extent of our knowledge of what is going on in mid-ocean it 

 is only necessary to think of such a fish as Ghiasmodon and its history. Ghiasmodon is 

 one of those grotesque looking pelagic fishes with yawning, flexible jaws and a vastly 

 distensible stomach, which is able to engorge other fishes equal, or more than equal, in size 

 to itself. This practice is naturally attended by disaster, and the Ghiasmodon, in the event 

 of death, is brought to the surface by the expansion of the gases in its tissues. Such 

 accidents evidently happen very often. The chances were few. nevertheless, that waifs of 

 this kind should fall into the hands of naturalists, and yet within forty years Ghiasmodon 



