October 6, 1911] 



SCIENCE 



449 



cations of form, structure and color as the 

 species became more and more modified by the 

 environment of the deep sea. We will confine 

 our attention to the modification of the colora- 

 tion and the relation between this and the dis- 

 tribution of the species. 



The Cyclogasteridse consist of about 100 

 species. The majority of these are placed in 

 three large genera. The genus Gyclogaster 

 consists of about 30, Careproctus of 38 and 

 Paraliparis of 21 species. The remaining 

 genera are monotypic or consist of a few spe- 

 cies. The vertical distribution and the color- 

 ation of the three large genera will be de- 

 scribed first. This will be followed by a chart 

 indicating the distribution and coloration of 

 all the species of the family. 



Before entering upon a discussion of the 

 genera it is advisable to review briefly the 

 factors which lend color to the different en- 

 vironments inhabited by these fishes. For 

 our purpose the color of a tide-pool environ- 

 ment may be said to be due to three factors 

 or groups of factors. These are : (1) sun- 

 light, (2) organisms and their remains, (3) 

 inorganic materials of which the bottom is 

 composed. In the tide-pools the coloration of 

 the second factor may appear to depend upon 

 the other two factors. In the oceanic depths 

 below the penetration of light and far above 

 the bottom these two factors are absent. The 

 color of the organic life, if protective, can not 

 be dependent upon their influence. It is 

 necessary to assume the presence of light other 

 than sunlight. We know that there is such 

 light as can be produced by light organs. It 

 has been suggested that there is another 

 source of light on the bottom of the ocean. 

 The decomposing animal matter may give off 

 a phosphorescent glow of such intensity that 

 the large-eyed fishes may be able to detect 

 objects. 



The modification of the color factors of the 

 environment is accompanied by a modification 

 of the coloration of the fishes. The sunlight 

 is more intense and the organic life more 

 brilliantly colored in the tide-pools and shal- 

 low waters of the tropics than in the arctic 

 regions. The difference in the intensity of 



the sunlight is accompanied by a difference in 

 temperature, but we shall ignore all the fac- 

 tors which compose an environment except 

 those that exhibit color. As we descend below 

 the surface of the ocean the sunlight becomes 

 less intense. The organic life becomes less 

 brilliantly colored. The red light rays prob- 

 ably do not penetrate below 500 meters or 273 

 fathoms. It has been suggested that this 

 depth marks the border between two differ- 

 ently colored faunas. Dr. Hjort found that 

 the fishes above this depth are characterized 

 by silvery sides and those below by black pig- 

 ment. The black forms are found nearer the 

 surface in northern latitudes. Where the 273- 

 fathom level touches bottom and where it is 

 far above bottom constitute two differently 

 colored environments. If at this level the 

 color of the bottom has an influence, then the 

 color of the fishes inhabiting these two en- 

 vironments should be different. It will be 

 shovm on the following pages that the bottom- 

 inhabiting species of eyclogasterids appear to 

 be differently colored from the free-swimming 

 forms. There is a certain depth in the ocean 

 below which light fails to penetrate. This 

 will be less in the arctic than in the torrid 

 regions. Its importance in marking the re- 

 gion between two faunas remains to be care- 

 fully worked out. 



Cyclogaster is a shallow water genus. The 

 species are coramon in the tide-pools and shal- 

 low cold waters of the northern and southern 

 hemispheres. At least 21 of the 30 species 

 have been taken in less than 10 fathoms. 

 Only 5 species have been taken from depths 

 below 100 fathoms and 3 from below 200 

 fathoms. One specimen has been taken at 

 250 fathoms. It is thus seen that the genus 

 is confined to the illuminated area of the 

 oceanic waters. We may provisionally place 

 the lower margin of the bathymetric distribu- 

 tion of the genus at the level at which Dr. 

 Hjort found the red light rays absent, the 

 500-meter or 273-fathom level. 



The species of the genus, with but three 

 exceptions, have a similar type of coloration. 

 The colors harmonize with those of the other 

 shallow-water fishes of northern regions. The 



