PREFACE 



a classical one, like Agassiz's "Poissons Fossiles," or Johannes Miiller's 

 "Myxinoiden," or is the most important one upon a subject, it is 

 printed in black face type. It is obvious, of course, that our estimate 

 of the value of a particular paper may not be just, but the general 

 reader will probably be willing to take chances, and in case he finds us 

 in error we must console ourselves with Newton's complacent dictum 

 that "it is impossible to print a book without faults." 



The sixth stage in preparing the Index was decided upon only after 

 numerous conferences : should the arrangement form a dry-as-dust con- 

 ventional index or should it be classified, with references so grouped 

 as to give the reader at one time and in one place materials for se- 

 lection. Of many headings, too, summaries and introductions were 

 recommended. This general procedure, it was agreed, would give an 

 encyclopedic value to our work, but it would also entail vast labor 

 upon our staff. It meant that the references of the bibliography in 

 their vast number be again sifted over, and many of them boiled 

 down for citation. Such a task the editors next attacked and they have 

 now brought it to a successful conclusion — cheered not a little by 

 the favorable comments of critical bibliographers — such a national 

 expert, for example, as Dr. Lydenberg of the New York Public Library 

 noting that a work on such lines "would have no parallel in the history 

 of science," — which is praise indeed! Certainly of no other branch 

 of the Animal Kingdom is there known to us as complete a compendium 

 of the literature or one so minutely digested for the reader. 



It became clear also that the sixth stage in the work, which assured 

 to it an Annotated Index, would have to be followed by a seventh, 

 which was to compile in the end an index of our index (VIII). This, 

 it was agreed, would prove more or less of a secretarial undertaking. 

 It meant, nevertheless, that the editors should indicate in the An- 

 notated Subject Index all words or themes which should be placed in 

 alphabetical order in the Final Index. Thus in the Subject Index, such 

 a theme as "Egg" should be considered in general and in detail, in 

 rebus membranes, yolk, nucleus, etc., and under each caption would 

 naturally appear many technicalia — but arranged in their natural, 

 not in their alphabetical order, e. g. permeability, micropyle, etc. But 

 even thus arranged these names would not be so scattered that the 

 reader would have trouble to find them; for he could pick them up at 

 definite pages in an alphabetical list at the end of the volume. 



There were certain guiding principles which were laid down during 

 the progress of the work: 



(a) Regarding species, genera and many families of living and fossil 

 fishes we could not attempt to cite purely systematic references in 



