THE CARP POND. 139 



whole northern hemisphere ; and his account 

 is one of the most instructive studies in the 

 geographical distribution of animals that has 

 yet been attempted. At the present day 

 these cyprinoids form one-third of all the 

 fresh-water species of fish known to science. 

 Yet they seem to be a comparatively modern 

 family, not being found in earlier geological 

 deposits than those of the tertiary age. 

 Apparently, the primitive ancestral carp was 

 evolved from some earlier species in the great 

 Himalayan range which divides the temperate 

 and tropical parts of Asia. This was a 

 splendid starting-place for a new family, since 

 the rivers which take their rise in the Central 

 Asian backbone ridge flow in every direction 

 towards the Arctic, the Pacific, and the Indian 

 Ocean, as well as towards the Aral Sea, 

 which once communicated with the Caspian, 

 and so gave access to the rivers of Russia. 

 The primitive cyprinoids accordingly set out 

 on their travels towards the plains on every 

 side ; and as they went they accommodated 



