OCEAN LIFE. 



81 



near relatives of the animals of past geological eras, it 

 being argued that the homogeneous temperature and 

 conditions of the ocean bottom would be favorable to 

 the persistence of antique forms. This theory has not 

 been sustained by the facts. While indications of an- 

 tiquity in some of the forms have been perceived, the 

 great mass of them approach the surface forms in 

 character, and present indications of originating in the 

 descent of such surface forms. The range of deep-sea 

 fishes is, indeed, very great. Certain forms which 

 live in shallow water in some regions have been 

 dredged from the greatest depths in others, and the 

 presumption is that littoral forms are capable without 

 great difficulty of adapting themselves to the widely 

 different conditions of deep-sea life. This may serve 

 also to explain the variety of colors of abyssal forms. 

 The fishes are usually of dark color, though some are 

 pink or silvery ; but many of the crustaceans are of 

 brilliant red hues, and the mollusks display consider- 

 able variety of coloration. Many of these animals, 

 moreover, display features of protective mimicry, and 

 others have burrowing habits. It is difficult to believe 

 that these characters have arisen from the exigencies 

 of a life passed in regions of darkness. They seem 

 rather to indicate that these animals are descendants 

 of surface forms, and have preserved some of their 

 original features and habits. 



There are two further things to consider : the food- 

 supply of these animals, and the modifications in 

 structure and mode of life necessarily resulting from 

 life in a region destitute of sunlight and subjected to 

 enormous pressure. In regard to food the active car- 

 nivorous forms, which include all the fishes, find an 

 abundant supply in the more sluggish creatures which 

 exist in such numbers. But the basis of all animal 

 life must be a vegetable diet, and there is no indication 

 of any plant forms gj-owing on the ocean bottom. 

 Plants need sunlight, if animals do not, and can only 

 exist within the reach of its influence. Yet it is not 

 difficult to ascertain the primary source of the deep-sea 

 food-supply. The surface of the ocean is crowded with 

 life, in extraordinary abundance and variety. In addi- 

 tion to the pelagic animals, minute algae exist abun- 

 dantly in the surface waters, and form the food of 

 many of the animal forms. This pelagic life remains 

 on the surface only during vitality. After death it 

 immediately begins to sink, and there is probably a 

 continuous rain of dead animals and plants descending 

 with some rapidity to the ocean-floor. These forms 

 possess considerable nutrient material, which probably 

 decomposes very slowly, and long remains fit for food. 

 It forms, as Dr. Carpenter remarks, a sort of broth, 

 which collects on the bottom, and furnishes an abun- 

 dant food-supply for the sluggish animals, which in 

 their turn yield food to the more active carnivora. It 

 is not difficult, therefore, to understand the existence 

 of an extensive fauna in a region destitute of plants. 

 The plant-life of the surface is the basts of the food 

 of deep-sea animals. 



The conditions of life in the depths of the ocean are 

 remarkably unlike those existing at the surface. The 

 ab-i;ne of sunlight is one radical distinction, and the 

 L'rvat pressure of the water is a second. At a thou- 

 -.iii' I fathoms this pressure is about one ton to the 

 square inch, and at the lowest depths reached it must 

 ! far more enormous. Yet there seems to be no 

 difficulty in sustaining this pressure. The tissues of 

 the animals are permeated with fluids, and the press- 

 ure, thus equalized, is probably not felt. Yet on 

 bringing them to the surface the effect of the sudden 

 diminution of prcs-ure is clearly seen, particularly in 

 the fishes, which often come up in a very dilapidated 

 condition. The tissues of the deep-sea fishes are, in- 

 deed, very fragile. The bones are often hht, fibrous, 

 and nearly destitute of calcareous material, so that 

 they may be penetrated by a sharp needle without in- 

 jury to ita point. The muscular sjvicin is also often 

 feebly developed, the muscles being thin and the con- 



nective tissue loose and feeble. It is probable that the 

 pressure may have something to do with these condi- 

 tions, the loose tissues being compressed so as to render 

 them serviceable for swift and vigorous motion. 



In addition to this characteristic of the tissues the 

 deep-sea fishes present many abnormal conditions of 

 structure, in some cases the head or the jaw being 

 enormously developed, while the body is reduced to a 

 ribbon form. Yet these strange creatures do not be- 

 long to new orders, but are simply modified varieties 

 of surface types. Their most striking modification, 

 however, is that due to the absence of natural light in 

 their habitat. Many of them are organized so as to 

 yield an artificial light to serve as lamps in their dark 

 abode while a corresponding variation in their eyes 

 has taken place. In certain cases their eyes are atro- 

 phied. Many of the gasteropoda, and some fishes and 

 crustaceans, have thus become blind. These belong 

 generally to antique types, and they often possess tactile 

 organs of gigantic size, touch supplying with them the 

 place of vision. _ But as a rule the eyes of deep-sea 

 animals are of increased size, and sometimes are de- 

 veloped to huge proportions, as if to enable them to 

 see well under conditions of very feeble illumina- 

 tion. 



The fact is that the habitat of these animals is far 

 from being the region of perpetual darkness which 

 might naturally be supposed. Very manv of the ani- 

 mals are self-luminous, this phosphorescence existing 

 alike in fishes, echinoderms, Crustacea, polyps, mol- 

 lusks, and annelids, the light yielded being perhaps 

 sufficient to diffuse a feeble illumination through the 

 thickly peopled regions of the ocean cavern. The con- 

 tents of the trawl, when drawn to the surface, are 

 often brilliant ly phosphorescent, many highly luminous 

 anthozoa, ophiurans, hydroids, crustaceans, etc. , yield- 

 ing their quota of light. The bottom seems to be 

 covered in some localities by forests of gorgonians, 

 which become luminous when disturbed by currents, 

 thus enabling the animals creeping or swimming 

 through them to see for some short distance. It is 

 supposed that this light may be protective, and in- 

 tended to warn foes not to come too near the danger- 

 ous lasso cells of the well-armed light-givers. 



The phosphorescent organs are not equally distrib- 

 uted among the various families of deep-sea fishes, 

 though those in which they are absent have usually a 

 well-developed muciferous system, tho abundantly 

 secreted mucus yielding the necessary luminosity. The 

 phosphorescent organs vary considerably, and are di- 

 vided into a number of classes. In one case the sides 

 of the fish are covered with innumerable minute 

 tubercles, raised above the skin, and supposed to be 

 light-givers. Secondly, we find tubercles of larger 

 size and less in number, which occur on the head as 

 well as on the body. Thirdly, eye-like spots appear, 

 white in preserved specimens but red or green in life. 

 These are ranged at regular intervals along the lower 

 sides of the body, and also occur on the head. Fourthly 

 are large, flat, round spots of a mother-of-pearl bright- 

 ness, which also extend in rows along the lower sides 

 of the body and head, while isolated ones appear in 

 other localities. Fifthly, more or less diffuse patches 

 of a white glandular substance, of varying thickness 

 and irregularly placed on the body, exist. There are 

 two or three other conditions and arrangements, though 

 the above given are the most important, and are suffi- 

 cient to show that an extraordinary provision for light- 

 ing up the depths of the ocean has been made. This 

 provision, with the unusual eye development, must 

 make the deep-sea a much more agreeable place of 

 abode than would naturally be expected. It is prob- 

 able that these luminous organs are at the command 

 of the fish, and are used to aid them in search of their 

 prey. The organs near the eyes, for instance, are sup- 

 posed to act on the principle of a bull's-eye lantern, to 

 project a beam of light ahead. In other cases where 

 :hc luminous organs are at the extremities of barbels 



