REPORT ON THE AMPHIPODA. xi 



suited for the purposes of later classifications, yet each remodelling requires to be tested 

 by that earliest form which is here reproduced. While every definition has been given 

 which claimed to refer to a new genus, references have also been made, wherever 

 available, to authorities who have disputed the claim of novelty, or to other reasonable 

 grounds for rejecting the defined name. When the type-species is well known, and speci- 

 mens of it have been examined by more than one competent observer, the true position 

 of a genus is comparatively easy to determine. But sometimes the solitary specimen on 

 which a genus was founded has since been lost or destroyed or damaged past recognition. 

 In some of these cases the genus remains either absolutely obscure or only the sport of 

 ingenious guesses. It would be convenient if some limit of time could be established, so 

 that after fifty or a hundred years the names which no one had been able to identify 

 throughout such a period should lose their right of priority. 



With species, as with genera, all that have ever been published as new ones are 

 admitted to the record. So far the task is simple. But here too an attempt has been 

 made, by references and suggestions, to guide the reader through the labyrinth of 

 synonyms. This part of the work is full of perplexity and complication, and the labour 

 here bestowed upon it can pretend to little more success than that of having drawn 

 into one view a large number of problems still requiring solution. Conjectural determina- 

 tions for or against the validity of a species, apart from observation of the actual 

 specimens described, must be accepted with much reserve even from the most experienced 

 writers ; for example, a consensus of important authorities had long referred Kr0yer's 

 Stegocephalus infiatus to Phipp's earlier Cancer ampulla, yet in 1887 Hansen decides 

 that Kr0yer's species is after all distinct. But the very fact that mistakes are so often 

 made in the attempt to regulate synonymy should at least have the useful result of 

 awakening attention to the extraordinary amount of trouble caused by vague and 

 inadequate descriptions, especially when these are given without explanatory figures of 

 the object described. 



In the general treatment of the large mass of literature here brought under review I 

 have desired as much as possible to save trouble to any naturalist who might in the 

 future have to deal with a collection similar to that which is the subject of this Eeport. 

 Hence brief notices of the Amphipoda and descriptions of single species embalmed in 

 large works have been quoted in full, and occasionally for the same reason short 

 separate treatises have received a longer notice than their intrinsic importance, apart 

 from their rarity, would have demanded. On the other hand, some works, such as the 

 British Sessile-Eyed Crustacea by Bate and Westwood, and Boeck's great work on the 

 Arctic and Scandinavian Amphipoda, have been only briefly noticed, since they are 

 already widely known and of necessity in general use, so that the enormous space 

 required for an exhaustive discussion of their contents would have been to a great extent 

 needlessly absorbed. Among the writings of the last century, attention should, I think, 



