12 The Life Story of the Fish 



animal descends from any other living animal j that, for 

 instance, the fish from which the amphibians descend is 

 extinct. The exponents of this theory received a shock when, 

 in 1938, fishermen dredged up from the ocean off the South 

 African coast a huge creature which was apparently a living 

 fossil — a fish which should have been extinct geologic ages 

 ago. For days after the news of this discovery ichthyologists 

 went around with expressions of astonishment and doubt on 

 their faces, asking each other if it were all a hoax. But when 

 this specimen at last reached the hands of a qualified palaeon- 

 tologist, he declared that not only was it undoubtedly a 

 species of living fossil, but that it was so close to fossil re- 

 mains and to the types which had been reconstructed there- 

 from that it could be positively identified as a member of 

 the coelacanths. Now, the coeJacanths are a group of fishes 

 which had branched off from the main evolutionary stem 

 before the amphibians appeared. Latimeriay as the new 

 discovery was named, is therefore not a living ancestor of 

 the amphibians, but a cousin of their ancestor's. 



And so it can still be truthfully said that no living form 

 descends from any other living form, at least insofar as 

 the major groups are concerned. But within the groups, and 

 above all within their narrower divisions, this is not true. 

 The world is not a finished job. The processes of evolution 

 are still going on, and nowhere is this more evident than 

 in some of the families of fishes. The trouts and salmons ^ 

 are an outstanding example: the great number of their spe- 

 cies and subspecies which scientists are still struggling to 

 sort out are the best possible indication that a single, for- 

 merly widespread animal is, under the influence of climatic 

 changes and geographical differences, in the very act of 



^ The plural form of these words is used to denote several species. We 

 say, "I caught four trout," but, "Among the trouts that spawn in the fall 

 are the brook and the brown." 



