Freshwater Crustacea of the Indian Archipelago. 239 



entirely abandoned an aquatic lite and was existing under 

 damp wood and stones. In the three other localities, each of 

 whicli furnished a new species, the creatures had already 

 become, at ;iny rate, amphibious, since they also existed under 

 stones at the edge of tlie water, similarly to our marine species 

 of (h-chestia, especially 0. ctivimana. No less a contrast to 

 European conditions is shown in the complete absence of 

 AsellidEe from the Malayan freshwaters. In their stead we 

 meet with quite a number of genuine marine Isopods, which, 

 however, are all parasites belonging to the families Cymo- 

 thoidas and Bopyrida3. Upon freshwater fishes in the Lake 

 of Singkarah 1 found Rocinela t?/pus, Milne-Edwards, and 

 Tacha^a lacustris, sp. n., the closest allied species to which 

 was discovered by von Martens upon the coral-reefs off 

 Singapore. In brooks and rivers far in the interior I met 

 with the peculiar species Ichthyoxenus Jellinghausii, Herklots, 

 upon Cyprinidffi, while Palgemonidse yielded seven species of 

 Bojjyrus. 



Can there possibly be a greater difference between the 

 European freshwater Crustacean fauna and that of the Indian 

 Archipelago ? To this we shall be obliged to reply in the 

 negative, and thus we come into conflict with the ever- 

 increasing inclination to attribute a similar character to the 

 freshwater faunaj of the globe. 



To account for this inclination, reasons very different in 

 value can be shown to exist. In the first place we have two 

 points, which apparently raiglit be left entirely to speak for 

 themselves : namely, the insufficient and incomplete state of 

 our knowledge of the local freshwater faunae of the earth, and, 

 further, the very imperfect determinations of the forms 

 discovered therein, which serve as the basis for reports and 

 communications in the form of generalizations upon the 

 freshwaters of foreign countries. While it is precisely in 

 such questions of animal distribution, which have a statistical 

 character, that it is impossible to have sufficient accm'acy in 

 the determination of the genus and species, a portion of the 

 literature dealing with freshwater faunae is of a very prelim- 

 inary kind, and could furnish nothing but altogether isolated 

 items of evidence in favour of the thesis that the fauna of 

 fresh water has a uniform character. Herein the one-sided 

 prominence given to the Invertebrates, and among these 

 again in the most marked degree to the groups with which 

 the European investigator is acquainted from the beginning, 

 plays a conspicuous part. 



These objections are not intended to obscure the fact that 

 an important nucleus of truth lies at the bottom of the 



17* 



