3 83 THE POPULAR SCIENCE MONTHLY. 



5. " With the Sunlight, Vegetable Life ceases in the Depths 

 op the Sea. All deep-sea fishes are therefore carnivorous ; the most 

 voracious feeding frequently on their own offspring, and the toothless 

 kinds being nourished by the animalcules which live on the bottom, or 

 which, 'like a constant rain,' settle down from the upper strata toward 

 the bottom of the sea. 



6. " The Perfect Quiet of the Watep* at Geeat Depths. 

 The agitation of the water, caused by the disturbances of the air, does 

 not extend beyond the depth of a few fathoms ; below this surface- 

 stratum there is no other movement except the quiet flow of ocean- 

 currents, and near the bottom of the deep sea the water is probably in 

 a state of almost entire quiescence." 



Now, the effect of these conditions on some part or parts of their 

 structure is such that all deep-sea fishes are easily recognizable, with- 

 out positive evidence of their having been caught at a great depthj 

 and in many of them the most striking characteristics relate to the 

 pressure of the water they inhabit. Their bones and muscles are com- 

 paratively feebly developed ; the former " have a fibrous, fissured, and 

 cavernous texture, are light, with scarcely any calcareous matter, so 

 that the point of a needle will readily penetrate them without break- 

 ing." They are loosely attached to each other the vertebrae es- 

 pecially ; and, unless carefully handled, the body will almost certainly 

 fall to pieces. But that this is not the animal's normal condition we 

 may be well assured. It is due simply to the absence of the pressure 

 which keeps the whole organization compact ; for, as has just been 

 stated, most of these fishes are rapacious, and to indulge their enor- 

 mous voracity they must execute rapid and powerful movements, to 

 effect which their muscles must be as firm and their vertebrae as tautly 

 braced as in their surface-swimming relatives. Marvelous as this is, 

 it is far from being all that is marvelous in the structure of these 

 dwellers in the profundities. Besides modifications of their eyes, such 

 as are found in several other groups of animals, many of them are fur- 

 nished with " more or less numerous, round, shining, mother-of-pearl- 

 colored bodies imbedded in the skin," of which Dr. Gtinther says : 

 " These so-called phosphorescent or luminous organs are either large 

 bodies of an oval or irregularly elliptical shape placed on the head, in 

 the vicinity of the eye, or smaller round globular bodies arranged sym- 

 metrically in series along the sides of the body and tail, especially near 

 the abdominal profile, less frequently along the back. . . . The organs 

 of one kind consist of an anterior, biconvex, lens-like body, which is 

 transparent during life, simple or composed of rods ; and of a poste- 

 rior chamber, which is filled with a transparent fluid, and coated with 

 a dark membrane composed of hexagonal cells or of rods arranged as 

 in a retina. . . . In the other kind the organ shows throughout a 

 simple glandular structure, but apparently without an efferent duct. 

 Branches of the spinal nerves run to each organ, and are distributed 



