X THE VOYAGE OF H.M.S. CHALLENGER. 



books and buying of books, how many journeyings to and fro, how many researches ending 

 in nothing, are necessarily involved in such consultation, those who have had a similar 

 experience will well know, and those who have not had it can scarcely be made to under- 

 stand. Without therefore expatiating on the difficulties which I suppose myself to have 

 conquered or on the difficulties which conquered me, it may suffice to mention that, as the 

 record proceeded, the plan of it was more than once changed, the earlier notices being 

 rewritten and expanded, under the influence of a growing desire that as much of the task 

 as possible should be done once for all and need no second doing. In the form actually 

 adopted, the titles of works are given in chronological order, so far as the year of publi- 

 cation is concerned, but within that year they for the most part follow the alphabetical 

 order of the authors' names.^ Accuracy in the dates given has been anxiously aimed at. 

 seeing that without this accuracy it is sometimes impossible to determine those questions 

 of priority on which scientific nomenclature so much depends. But precision is very 

 difficult to arrive at, when the only available copy of a work is an undated extract from 

 a foreign magazine, or from the proceedings of a learned society, read in one year and 

 published in the next or the next but one. It is greatly to be wished that " separate 

 copies" should not only have the true paging, as Darwin^ urges, but that they should 

 also have that date of jjublication from which the new genera and .species contained in 

 them have a claim to reckon their priority. 



The title of each work mentioned in the Bibliography is accompanied, it will be seen, 

 as a rule by some notice of its contents. There are a few exceptions, where papers, of 

 which the titles could be cited on adequate authority, have remained inaccessible, or 

 where the titles themselves seemed sufficiently stiggestive without further comment. 

 Here and there, like a sign-post with the legend " No Road " upon it, the title of a book 

 has been given for the sake of saying that it contains nothing about the Amj)hipoda. 

 On the other hand some obscure works, perhaps really bearing on the subject, are omitted 

 from the general list and only incidentally referred to as occasion offered. In the notices 

 taken collectively two special objects have been aimed at : — 



1. To quote the original definition of every genus of the Amphipoda. 



2. To give under its j)roper date the name of every new species. 



Two objects of a more general character have also been kept in view, namely, first, 

 to give some idea of the character of the information which the various writings supply, 

 and secondly, in so doing to produce a record, after the annalistic method, of the progress 

 of knowledge in this branch of natural history. 



It will be readily understood that a generic definition as at first framed is often little 



' The following names are exceptions to the alphabetical order on the pages mentioned : — Seba, Linnaeus, p. 18 

 Linnaius, p. 20 ; Str0m, p. 28 ; Olafsen, p. 36 ; Ginnani, Hammer, p. 38 ; Fabricius, p. 40 : Pallas, p. 41 ; T'orskal, p. 43 

 de Quironic, p. 47; Linnaeus, p 53; Roemer, p. 55; Pallas, p. 65; Latreille, p. 71 ; Rafinesque, p. 87; Leach, p. 89 

 Pollini, de Blainville, p. 93 ; Leach, p. 107; Costa, Kr0yer, p. 177; Kraus, p. 205; Bate and Westwood, p. 340; Ger- 

 staecker, p. 342 ; Cunningham, p. 404. 



- The Life and Letters of Charles Darwin, edited by his son, Francis Darwin, vol. iii. p. 141. 



