EEPOET ON THE DEEP-SEA FISHES. xxi 



Lowe as .well as Jolmson deposited their treasures in the British Museum, and from 

 these materials chiefly I formed the idea of a special adaptation of the ichthyic type to 

 Imthybial life. The comparison of fishes so widely different as Plagyodus {Ale2ndo- 

 saurus), Eegaleacs, Tr achy icterus, Stylophorus, Saccopharynx, Chiasmodus, Melano- 

 cetus, showed nevertheless a singular agreement in important points of organisation, 

 and even in the circumstances under which their capture took place. And having 

 recognised that the diminished amount of earthy matter in the osseous system, the 

 extreme thinness of the muscular layers of the trunk and tail, the easily ruptured 

 connective ligaments and tissues of the muscles and bones, the increase in size or 

 degradation of the organ of sight, the distensibility of the stomach, the shrinking of 

 the gills, the development of the muciferous system with or without special organs of 

 '■•luminosity, the black coloration of the pharynx and peritoneum, were peculiarities 

 which, either singly or combined, either by themselves or in connection with other 

 evidence, indicated the bathybial nature of the fish, I relegated to tlie deep-sea fauna 

 Plagyodus in 1860, the Trachypteridse and Lophotidae in 1861, Halargyreus and 

 Saccopharynx in 1862, Melaviphaes, Melanocetus, Chiasmodus, a part of the Sternopty- 

 chidse, Scopelidas and Stomiatidse in 1864, the Halosauridse in 1866, Pseudophycis in 

 1867, and Synaphobranchus in 1870.^ 



I had no definite information at the time with regard to the depth at which these 

 types habitually live, but I thought it probable that some of them descend to much 

 greater depths than were recorded hitherto, and that the degree of adaptation to a 

 bathybial life increased with the depth reached by the fish ; in fact, that the successive 

 vertical zones of the deep sea were inhabited by fishes of a different and peculiar 

 organisation. This last surmise has not been verified by the facts obtained during the 

 Challenger and subsequent expeditions. But I ascertained, at a time previous to the 

 British Deep-Sea expeditions,^ that deep-sea fishes must have a wide horizontal range, 

 and that consequently the physical conditions of the depths of the ocean must be the 

 same or nearly the same over the whole globe, — a fact already recognised by Risso, 

 though his observations were limited to the district of the Gulf of Genoa (vide supra, 

 p. xix.). 



The materials brought home by the Challenger laid a .broad and sure foundation 

 of our knowledge of the abyssal fish-fauna, and the preliminary notices of the new and 

 remarkable forms which were published in the years 1877 and 1878^ could not fail to 

 draw the attention of the succeeding explorers of the deep sea to this class of animals. 



1. Of the three Norwegian North Atlantic expeditions undertaken in the years 

 1876, 1877, and 1878, the last furnished much information as regards the deep-sea 



1 See Cat. Fish., under the headings of the genera enumerated ; Proc. Zool. Soc. Land., 1864, p. 301 (^Melanocetus); 

 Proc. Zool. Soc. Land., 1866, p. 336 (Ausonia). 



» Cat. Fish., vol. v. p. 420, 1864. ^ ^,j„_ ^nd Mag. Nat. Hist., 1877, vol. x.\., and 1878, vol. ii. 



