IOO 



DISCOVERY REPORTS 



kidneys. But as both gills and kidneys in bathyphilum are greatly reduced, there can be little doubt 

 that denudatum is the more highly organized and active species. 



The species of Cyclothone also live at different levels in the ocean. C. braueri, a light-coloured 

 species, occurs mainly between 500 and 1000 m., while the populations of the black species (livida, 



• • • B 





A' 



B' 



fb 



mb 



cb 



B" 



Text-fig. 42. Comparison of the external appearance, gill development and brain of Gonostoma denudatum atlantkum (a a', a") 

 and G. bathyphilum (b, b\ b""). The gill filaments shown in (a') and (b') are from the second gill arch, fb, forebrain; mb, m.d- 

 brain; cb, cerebellum, (a and B, X075; a' and b', x 12-5; a" and b", x 5.) 



