1885.] 



CLADOCERA. 



7 



Cladoceran Fauna is quite uniform ; and of late years it has, too, 

 been clearly shown by the investigations of Sign. Pavesi, that 

 even the Cladocera of Italy are represented by precisely the 

 same species as those occurring in Norway and existing under 

 conditions in every respect similar, some of them being restric- 

 ted to small ponds, whereas other forms are met with in lakes, 

 swarming in the middle water and thus presenting a counter- 

 part to the so-called pelagic animals of the Ocean. To afford a 

 sufficient explanation of so wide and extraordinary distribution 

 of fresh-water species, we must, I think, admit the accidental 

 transmission of winter-eggs, by the aid of migratory birds 

 of the orders Grallatores and Natatores, essential importance. 

 Considering the great facility with which eggs of Entomostraca 

 will adhere to the feet of such birds along with some portion 

 of mud from the ponds or lakes they frequented immediately 

 previous to commencing their long migratory flight, we may in 

 truth be fully entitled to admit the great probability of such 

 transmission of ova from far-off tracts. Now, we meet in all parts 

 of the world — let alone stationary birds — with such that under- 

 take at least short flight of passage; and hence it should seem 

 not altogether improbable, that at times there is, or has been, 

 a certain continuity between the faunas of Cladocera even in 

 two localities so widely distant as Norway and the tropical part 

 of Australia, though at present, in all probability, none of the 

 species occurring in the latter region can, in a strict sense, be 

 specifically indentified with any Norwegian forms. 



As is well known, our acquaintance with the Cladocera has 

 been almost exclusively derived from investigations instituted 

 in Europe; whereas the contributions to the natural history of 

 these interesting little Crustaceans yielded from other quarters 

 of the globe 1 are for the most part both very scant and the 



1 As regards the Cladocera of Australia, some notices have been puhlished by 

 Mr. King in the Proceedings of the Koy. Society of Van Diemensland for 

 1853. on the species occurring in New South Wales. I do not myself know 

 this Memoir except from an abstract given by S c h o e d e 1 e r in his paper : „Z\a 

 Xaturgeschichte der Daphniden" (1877), in which also some of the figures 



