1000 



SCIENCE. 



[N. S. Vol. XIV. No. 365. 



Light-producing organs may be found, often 

 in great numbers, in various parts of the body. 

 Often such organs are coordinated with eyes, 

 and in some cases — e. g. , Ipnops* — the eye itself 

 has become degenerate and replaced by a phos- 

 phorescent organ. Among the crabs, as well as 

 fishes, the light-emitting organs serve as dark- 

 lanterns to illuminate the immediate surround- 

 ings, and also as lures to attract the prey. The 

 author claims that there is, in general, a de- 

 creasing degeneration of the eye with increas- 

 ing depth. In Ethusa granulata, a crab, speci- 

 mens from shallow water have good visual 

 organs, while those from 900 to 1,300 m. are 

 usually blind. It appears to be a fact that the 

 eyes of deep-sea forms tend either to a great 

 increase in size, on the one hand, or degenera- 

 tion on the other, as ordinary eyes are of little 

 use in the depths. 



The possession of light-emitting organs in 

 blind animals is explained on the ground of 

 utility in terrifying hostile animals or alluring 

 the prey.f There are also instances in which 

 very similar light-producing organs have been 

 developed by widely differing animals by a 

 process of approximation. 



In discussing the systematic relationships of 

 deep-sea animals the author states that they do 

 not differ among themselves more than do shal- 

 low-water forms. It was at first thought that 

 the abyssal region would yield many ancient 

 types, and, indeed, this is in a measure true. 

 It appears that the older forms were often 

 driven to the depths to escape competition with 

 newer and more specialized rivals. Many deep- 

 sea sponges and echinoderms resemble creta- 

 ceous and Jurassic types. It can be stated as a 

 generalization, however, that deep-water ani- 



* It should be noted, however, that the eyes of Ip- 

 nops still appear to be functional, although exceed- 

 ingly modified to form the immense phosphorescent 

 lantern that occupies about half of the dorsal surface 

 of the head. 



t In the discussion of phosphorescence in the deep 

 sea, the conclusions of Professor Seeliger are so nearly 

 identical with those presented by the present writer 

 in the number of Science issued May 31, 1901, that 

 attention should he called to the note at the bottom 

 of page 852, referring to a previous article on ' The 

 Utility of Phosphorescence in Deep-sea Animals,' 

 published in the American Naturalist, Oct., 1899. 



mals are no nearer mesozoic forms than are 

 those from lesser depths. In sustaining this 

 latter claim the author cites the many cases of 

 so-called ' living fossils ' among shallow water 

 mollusks, and also the old-fashioned mammals 

 still existing, such as the proboscidians. On 

 the other hand, deep-sea' animals can often, in- 

 deed usually, be referred to existing genera of 

 shallow-water forms, and the author claims that 

 the former were originally derived from the 

 shallow-water inhabitants of the past. The 

 conditions of life in the abyssal regions are not 

 conducive to developmental changes, neither 

 are they such as to favor the evolution of the 

 organic from the inorganic. 



Professor Seeliger, like most other writers on 

 this subject, cannot refrain from having his 

 fling at the ' Bathybius theory ' of Huxley, 

 which was exploded through the chemical re- 

 searches of Buchanan, who demonstrated that 

 the apparently vital movements of ' Bathyhius ' 

 were purely physical. 



Our author believes that animal life becomes 

 less abundant in the greater depth, but that 

 there is no zone that is entirely uninhabited, a 

 conclusion directly opposed to the one so thor- 

 oughly demonstrated by Alexander Agassiz, who 

 maintains that there is an intermediate zone 

 which is practically lifeless. The argument 

 against the existence of an uninhabited zone is 

 based on considerations affecting the food sup- 

 ply. In shallow water the food basis is largely 

 vegetable, but plant life becomes sparse below 

 200 m. and practically vanishes below 400 m. 

 But the inhabitants of the underlying zone as- 

 cend to what may be called the plant zone for 

 their nourishment, and then retire satisfied to 

 the deep. The bottom-inhabiting species, 

 whether free-moving or fixed, are nourished by 

 the organic substances sinking, in changed 

 form, to the bottom. 



The bottom deposits are briefly described as 

 diatom ooze, radiolarian ooze, globigerina ooze 

 and red clay. 



The author concludes by emphasizing the in- 

 timate connection between the animal inhab- 

 itants of the upper and deeper zones, and the 

 dependence of the abyssal forms upon the upper 

 regions for their food supply. The animal 

 world of the deep is in general a reflected rep- 



