FOSSILS AND PEDIGREES 341 



existence. There arc innumerable other branches, some short 

 and simple, others long and further branched, representing forms 

 that have flourished for a time but finally passed away: of 

 these, some failed to adapt themselves to changed conditions 

 and so perished, others became variously changed and modified, 

 to give rise to new and perhaps more successful types. 



The main diverging branches of such a genealogical tree are 

 called phyla, and the term phylogeny is applied to the study 

 of the pedigrees of living animals, as opposed to ontogeny, 

 concerned with the development of the individual from the 

 egg to the mature animal : the one deals with the history of the 

 race, the other with the history of the individual. The business 

 of the systematic zoologist is to study and compare the existing 

 fishes, in an endeavour to make out their aflfinities one to the 

 other, and to discover the lines of descent that connect the various 

 branches of the "tree" upon which his classification is based. 

 A perfect taxonomy is one that would express all the known 

 facts in the evolution and development of the various forms. 

 The evidence upon which it would be based would be drawn 

 mainly from two sources, namely, comparative anatomy and 

 embryology, but there is a third science which provides definite 

 and irrefutable evidence of the truth of racial evolution. This, 

 the science of palaeontology, is concerned with the remains of 

 extinct animals and plants buried in the rocks, and no scheme 

 of classification, nor any genealogical tree that may be composed 

 to illustrate the lines of descent of a particular group of animals, 

 is worthy of serious consideration until it has been tested by a 

 study of the record provided by the rocks. It is reasonable to 

 suppose that if, as every scientific man believes to-day, evolution 

 is an established theory and not a mere hypothesis, the series 

 of fossils excavated by the palaeontologist should provide some 

 evidence of this process, and that it should be possible to recon- 

 struct from these remains, if not some of the ancestral types 

 themselves, at least some of their near relations. To give any 

 sort of detailed account of the large number of fossil fishes 

 that have now been described would be altogether beyond the 

 scope of this work, and it will be possible only to survey very 

 briefly some of the more interesting forms, and to consider 

 their affinities with living fishes. 



As the result of many years of study of the organic remains 

 contained in the fossil-bearing rocks of the world, most of these 

 rocks have now been assigned to their correct place in the 

 geological record, and the history of the earth has been split 



