462 



THE VOYAGE OF H.M.S. CHALLENGER. 



If the number of species of both divisions be computed for bathymetrical regions of 

 500 fathoms, and without reference to the first 94 fathoms, then the statistics read as 

 follows : — 



From the above this fact is distinctly evident that the Dictyonina show a much 

 more rapid decrease of species downwards than do the Lyssacina. The percentage 

 figures of the latter over the whole, from 95 to 3000 fathoms, vary from 20 to 37 per 

 cent, while the percentages of the Dictyonina over the same range decrease somewhat 



