6 POPULAR SCIENCE MONTHLY. 



In a perfect taxonomy, or natural system of classification, animals 

 would not be divided into groups nor ranged in linear series. We 

 should imagine a series variously and divergently branched, with each 

 group at its earlier or lower end passing insensibly into the main or 

 primitive stock. A very little alteration now and then in some struc- 

 ture is epoch-making and paves the way through specialization to a new 

 class or order. But each class or order through its lowest types is inter- 

 tangled with some earlier and otherwise diverging group. A sound 

 system of taxonomy of fishes should be an exact reflex of the history 

 of their evolution. But in the limitations of book making, this tran- 

 script must be made on a flat page, in linear series, while for centuries 

 and perhaps forever whole chapters must be left vacant and others 

 dotted everywhere with marks of doubt. For science demands that 

 positive assertion should not go where certainty can not follow. 



A perfect taxonomy of fishes would be only possible through the 

 study, by some Artedi, Miiller, Cuvier, Agassiz, Gill or Traquair, of 

 all the structures of all the fishes which have ever lived. There are 

 many fishes now living in the sea which are not yet known to any nat- 

 uralist. • Many others are known to one or two, but not yet accessible to 

 those in other continents. Many are known externally from specimens 

 in bottles, or drawings in books, but have not been studied thoroughly 

 by any one, and the vast multitude even of the species have perished 

 in Paleozoic, Mesozoic and Tertiary seas, without leaving a tooth or 

 bone or fin behind them. With all this goes human fallibility, the 

 marring of our records, such as they are, by carelessness, prejudice, 

 dependence and error. Chief among these are the constant mistakes of 

 analogy for homology, and the inability of men to trust their own eyes 

 as against the opinion of the greater men who have had to form their 

 opinions before all the evidence was in. 



The result is, again to quote from Dr. Coues : 



That the natural classification, like the elixir of life or the philosopher's 

 stone, is a goal far distant. 



It is obvious that fishes, like other animals, may be classified in num- 

 berless ways, and, as a matter of fact, by many different men they have 

 been classified in all sorts of fashions. 



Systems have been based on this or that set of characters, and erected from 

 this or that preconception in the mind of the systematist. . . . The mental 

 point of view was that every species of bird (or of fish) was a separate creation, 

 and as much of a fixture in nature's museum as any specimen in a naturalist's 

 cabinet. Crops of classifications have been sown in the fruitful soil of such 

 blind error, but no lasting harvest has been reaped. . . . The genius of modern 

 taxonomy seems to be so certainly right, to be tending so surely, even if slowly 

 in the direction of the desired consummation, that all differences of opinion, 

 we hope, will soon be settled, and defect of knowledge, no perversity of mind 

 will be the only obstacle in the way of success. The taxonomic goal is not 



