GENERAL BIOLOGY 687 



e represents the head of Ipnops vmrrayi, Gthr., taken by 

 the " Challenger" in about 3000 metres. 



a shows a "normal" eye like the eyes of bottom-fishes on 

 the slopes of the coast banks ; b and c exhibit very small 

 eyes; finally, d and e are perfectly blind. In Bathymicrops 

 the whole head is covered with scales, including the eyes, 

 which are only faintly visible through the covering as minute 

 black dots. In Ipnops the head is covered with filmy bony 

 plates, and eyes are entirely absent. A peculiar organ, which 

 has been regarded as a light-organ, is situated below the 

 plates, and supposing this interpretation to be correct it is the 

 only light-organ known in these forms, ^ 



How is this series of remarkable forms to be arranged con- 

 formably to the biological classification of the fishes accord- 

 ing to their light - organs attempted above } They have all 

 been taken only in the trawl, but are they really bottom fish ? 

 Why then (if we may be allowed the expression) do they not 

 all possess large eyes, like other bottom fish living at similar 

 depths .^ On the other hand, we must admit that they all differ 

 from pelagic fishes in appearance. Most bathypelagic fishes 

 are black, and their scale covering is but poorly developed. 



As a " working hypothesis " I would suggest that these 

 fishes belong to the deepest water-layers near the ocean-floor, 

 and for this reason they unite qualities characteristic of both 

 bottom fishes and pelagic fishes. The fact that they belong 

 to the family Scopelidae seems to strengthen this view, 

 as this family comprises such a wealth of pelagic forms. 

 Several of these fishes, as for instance Benthosaiirus grallator 

 (Fig. 502), are also provided with long filaments or whip- 

 like appendages indicating pelagic habits ; to the south of the 

 Azores we took some splendid specimens, in which these 

 appendages, really transformed fin-rays, were intact, as seen in 

 the figure. 



Another problem attaches to the remarkable fact, previously peiagic fishes 

 mentioned, that li2:ht-orQ:ans are lackino^ in all pelagic fishes o{°^^^^'^^ 



o& fc> rfc) waters and 



the coast waters and also of the boreal area. Neither are they of the 

 found in the fishes of tropical coast waters, where the temperature ^^"^^^^ '^'■''''• 

 cannot be supposed to prevent their development, nor do they 

 occur in those of the Norwegian Sea, where the depth is sufficient 



^ Sir John Murray and Professor Moseley at first described these organs as modified eyes, — 

 without lens or vitreous humour, and with only rods arranged in hexagonal bundles in the retina. 

 Later Moseley stated they were certainly not eyes, but phosphorescent organs (see Manchj 

 Science Lectures, Dec. i8, 1877, P- 132 ; Narr. Chall. Exp., vol. i. p. 239, 1885 ; Zool 

 Exp., Part LVII. Appendix A, 1887). 



